1 00:00:42,080 --> 00:00:47,720 All life in the oceans depends on the continuous movement of water. 2 00:01:01,040 --> 00:01:03,360 There are not five separate oceans on Earth... 3 00:01:04,880 --> 00:01:06,400 ..but just one... 4 00:01:06,400 --> 00:01:10,800 ..whose parts are linked by powerful, unceasing currents. 5 00:01:13,000 --> 00:01:17,200 Every drop of seawater on Earth rides these currents, 6 00:01:17,200 --> 00:01:21,520 taking a thousand years to complete a single circuit. 7 00:01:25,040 --> 00:01:27,680 And where there are currents... 8 00:01:27,680 --> 00:01:29,440 ..there is life. 9 00:01:46,440 --> 00:01:48,720 Off the coast of South Africa, 10 00:01:48,720 --> 00:01:50,440 dolphins are on the hunt. 11 00:02:01,280 --> 00:02:04,280 They have found a cold-water current 12 00:02:04,280 --> 00:02:07,440 and are now travelling along it looking for food. 13 00:02:10,760 --> 00:02:13,080 Gannets follow them. 14 00:02:14,840 --> 00:02:18,680 They know that doing so is the fastest way to a meal. 15 00:02:24,480 --> 00:02:26,160 A shoal of mackerel... 16 00:02:26,160 --> 00:02:28,520 ..just what the dolphins have been looking for. 17 00:02:35,320 --> 00:02:39,160 They encircle the fish, driving them into a bait ball, 18 00:02:39,160 --> 00:02:41,480 and then trap them against the surface 19 00:02:41,480 --> 00:02:43,840 to prevent them from escaping to deeper water. 20 00:02:49,360 --> 00:02:53,280 Now, the fish are within range of the dive-bombing gannets, 21 00:02:53,280 --> 00:02:55,560 who hit the water at 50mph. 22 00:03:19,440 --> 00:03:23,480 A sudden gathering of thousands of predators brought together 23 00:03:23,480 --> 00:03:26,480 by the flow of currents. 24 00:03:41,960 --> 00:03:44,840 Last to the feast are sharks. 25 00:04:07,720 --> 00:04:10,240 In these vast, open waters, 26 00:04:10,240 --> 00:04:14,640 finding food would be all but impossible without currents... 27 00:04:15,600 --> 00:04:19,320 ..the highways of the seas that bring this life together. 28 00:04:24,200 --> 00:04:27,280 When the bait ball has been dispersed, 29 00:04:27,280 --> 00:04:31,080 all that is left are scales drifting downwards. 30 00:04:36,080 --> 00:04:40,120 They are part of a slow, never-ending blizzard 31 00:04:40,120 --> 00:04:45,320 of organic waste that eventually settles on the sea floor. 32 00:04:48,320 --> 00:04:51,560 But it doesn't stay here forever. 33 00:04:51,560 --> 00:04:55,120 The currents sweep it back up into the sunlit surface waters... 34 00:04:56,440 --> 00:04:59,960 ..where it nourishes clouds of phytoplankton... 35 00:05:02,240 --> 00:05:07,120 ..simple microscopic plants that are the pastures of the seas. 36 00:05:16,840 --> 00:05:19,680 There are thousands of different kinds, 37 00:05:19,680 --> 00:05:25,200 and together they produce half of all the oxygen in the atmosphere... 38 00:05:25,200 --> 00:05:29,360 ..more than all our forests and jungles combined. 39 00:05:31,520 --> 00:05:33,960 And, by absorbing carbon, 40 00:05:33,960 --> 00:05:38,000 they are our greatest ally in combating climate change. 41 00:05:43,400 --> 00:05:48,800 Plankton are the foundation of almost all life in the ocean, 42 00:05:48,800 --> 00:05:51,760 for, in those places where the currents bring nutrients 43 00:05:51,760 --> 00:05:55,600 to the surface, they multiply in astonishing numbers... 44 00:05:57,280 --> 00:05:59,560 ..turning the ocean green. 45 00:06:05,720 --> 00:06:10,560 The currents travelling through our oceans bring life to seas 46 00:06:10,560 --> 00:06:13,720 that would otherwise be marine deserts. 47 00:06:18,120 --> 00:06:22,360 The Galapagos Islands lie in the path of one of them, 48 00:06:22,360 --> 00:06:24,640 the deep-flowing Cromwell Current 49 00:06:24,640 --> 00:06:27,640 that runs for 6,000 miles across the Pacific. 50 00:06:31,760 --> 00:06:34,360 As it approaches Fernandina Island, 51 00:06:34,360 --> 00:06:37,720 it rises and delivers nutrients into its shallows. 52 00:06:50,960 --> 00:06:56,200 And it also brings life to this otherwise barren island. 53 00:07:13,640 --> 00:07:15,560 Iguanas. 54 00:07:17,160 --> 00:07:19,200 There are thousands of them. 55 00:07:26,760 --> 00:07:31,040 And yet there's nothing on the island for these vegetarians to eat. 56 00:07:33,720 --> 00:07:36,120 Or... 57 00:07:36,120 --> 00:07:37,440 ..almost nothing. 58 00:07:39,760 --> 00:07:44,440 Cormorants bring seaweed ashore with which to make their nests. 59 00:07:46,000 --> 00:07:49,000 But what is building material for a cormorant 60 00:07:49,000 --> 00:07:51,520 is food for an iguana. 61 00:07:57,480 --> 00:08:00,280 Both these species evolved here, 62 00:08:00,280 --> 00:08:03,200 but that doesn't necessarily make them good neighbours. 63 00:08:08,200 --> 00:08:09,520 No matter. 64 00:08:09,520 --> 00:08:12,200 He knows where there's more elsewhere. 65 00:08:14,320 --> 00:08:15,920 He's a marine iguana... 66 00:08:21,160 --> 00:08:23,480 ..the only lizard in the world 67 00:08:23,480 --> 00:08:25,320 that gets its food from the sea. 68 00:08:38,120 --> 00:08:40,920 The seaweed on which he totally relies 69 00:08:40,920 --> 00:08:43,200 only grows in abundance here 70 00:08:43,200 --> 00:08:46,880 because of the nutrients brought by the Cromwell Current. 71 00:08:53,600 --> 00:08:57,640 Once in the water, he has just 30 minutes to find food. 72 00:09:06,000 --> 00:09:07,800 Any longer than that, 73 00:09:07,800 --> 00:09:10,760 and his muscles will seize up and he'll drown... 74 00:09:12,200 --> 00:09:16,200 ..for, like most reptiles, he can't handle the cold. 75 00:09:25,120 --> 00:09:29,000 Chilly water isn't a problem for a warm-blooded cormorant. 76 00:09:30,720 --> 00:09:33,080 She can swim in it all day, 77 00:09:33,080 --> 00:09:35,600 but can only hold her breath for a few minutes. 78 00:09:42,920 --> 00:09:44,960 He, on the other hand, 79 00:09:44,960 --> 00:09:47,520 completes his whole half-hour trip 80 00:09:47,520 --> 00:09:49,680 on one single breath. 81 00:09:51,600 --> 00:09:54,040 His flat face and sharp teeth 82 00:09:54,040 --> 00:09:57,280 make him an efficient seaweed-cropping machine, 83 00:09:57,280 --> 00:10:00,040 but with the clock ticking, he must eat fast. 84 00:10:04,440 --> 00:10:06,960 The cormorant, having caught its fish... 85 00:10:07,960 --> 00:10:09,480 ..goes back to the surface. 86 00:10:12,080 --> 00:10:14,000 One last mouthful, 87 00:10:14,000 --> 00:10:17,160 and it's also time for the iguana to head for home. 88 00:10:20,560 --> 00:10:24,240 But to stop his muscles from seizing up in the cold water, 89 00:10:24,240 --> 00:10:25,920 he must get back quickly. 90 00:10:30,360 --> 00:10:32,800 So he could do without the attentions 91 00:10:32,800 --> 00:10:34,800 of an inquisitive sea lion. 92 00:10:58,040 --> 00:11:00,480 Dry land is now just 30 metres away, 93 00:11:01,880 --> 00:11:04,840 but the biggest hurdle is still to come. 94 00:11:14,560 --> 00:11:17,600 The surging water now fights against him. 95 00:11:24,680 --> 00:11:28,560 He's out, but he's stayed in the cold so long 96 00:11:28,560 --> 00:11:30,200 that he's lost his strength. 97 00:12:11,480 --> 00:12:13,280 And he's made it. 98 00:12:16,080 --> 00:12:20,000 Few reptiles on the planet have to work harder for a meal 99 00:12:20,000 --> 00:12:21,440 than he does. 100 00:12:24,160 --> 00:12:27,920 And, tomorrow, he'll have to do it all over again... 101 00:12:30,440 --> 00:12:32,680 ..unless next time... 102 00:12:32,680 --> 00:12:34,480 ..he can outwit his neighbour. 103 00:12:40,480 --> 00:12:43,440 Over 100,000 marine iguanas live on Fernandina... 104 00:12:45,920 --> 00:12:49,680 ..and each owes its existence to the Cromwell Current 105 00:12:49,680 --> 00:12:51,840 that brings nutrients to these shores. 106 00:12:54,400 --> 00:12:58,080 But there is another, much bigger, current 107 00:12:58,080 --> 00:13:02,400 which carries water from the Pacific into the Indian Ocean. 108 00:13:05,520 --> 00:13:10,440 On this great journey, it travels through the islands of Indonesia, 109 00:13:10,440 --> 00:13:13,240 bringing together life from both oceans. 110 00:13:20,680 --> 00:13:24,880 A third of all the world's reef fish live here. 111 00:13:28,680 --> 00:13:31,640 Some call it the Coral Triangle, 112 00:13:31,640 --> 00:13:34,760 the most diverse marine region on Earth. 113 00:13:43,160 --> 00:13:46,960 The variety here is dazzling, not just of coral, 114 00:13:46,960 --> 00:13:48,840 but of animals of all kinds. 115 00:13:59,280 --> 00:14:03,720 Few are stranger than the flamboyant cuttlefish. 116 00:14:07,120 --> 00:14:10,760 This is a male, just five centimetres long. 117 00:14:15,920 --> 00:14:20,360 Swimming against the current isn't easy when you're small, 118 00:14:20,360 --> 00:14:23,120 so, instead, he prefers to walk... 119 00:14:25,000 --> 00:14:27,040 ..very, very slowly. 120 00:14:31,560 --> 00:14:34,280 He's a master of camouflage. 121 00:14:34,280 --> 00:14:37,040 But, right now, he wants to be noticed. 122 00:14:40,240 --> 00:14:42,320 He's looking for a mate. 123 00:14:43,760 --> 00:14:47,040 His potential partner is a giant, by comparison, 124 00:14:47,040 --> 00:14:48,520 four times his size. 125 00:14:53,760 --> 00:14:55,960 When it comes to courtship, 126 00:14:55,960 --> 00:14:58,520 being flamboyant isn't enough. 127 00:15:04,600 --> 00:15:06,920 To win her over, he must dazzle. 128 00:15:14,160 --> 00:15:17,640 His aim is to deposit a packet of sperm 129 00:15:17,640 --> 00:15:19,560 inside her mouth. 130 00:15:22,920 --> 00:15:25,160 Close... 131 00:15:25,160 --> 00:15:26,560 ..but no cigar. 132 00:15:32,320 --> 00:15:34,680 He'll have to turn up the dazzle. 133 00:15:41,680 --> 00:15:43,120 Take two. 134 00:15:47,920 --> 00:15:49,200 Bingo! 135 00:15:59,720 --> 00:16:01,960 His job is done. 136 00:16:01,960 --> 00:16:05,200 Now she must find somewhere to lay their eggs. 137 00:16:08,320 --> 00:16:11,120 An old shell will do nicely 138 00:16:11,120 --> 00:16:14,040 if she can slip past the present occupant. 139 00:16:19,160 --> 00:16:22,800 She fastens her eggs to the underside of the shell, 140 00:16:22,800 --> 00:16:25,000 where they'll be safe from predators. 141 00:16:38,680 --> 00:16:43,200 The current that brings so much life to the Coral Triangle 142 00:16:43,200 --> 00:16:46,920 now washes the eggs with clean, oxygenated water. 143 00:16:53,600 --> 00:16:57,360 After just three weeks, they start to hatch. 144 00:17:02,040 --> 00:17:04,160 Smaller than a human fingernail, 145 00:17:04,160 --> 00:17:07,520 the hatchlings are now carried by the current 146 00:17:07,520 --> 00:17:09,480 to other parts of the reef. 147 00:17:17,600 --> 00:17:19,920 And, in just a few months, 148 00:17:19,920 --> 00:17:24,120 this young male will be ready to find a female of his own. 149 00:17:30,200 --> 00:17:33,120 By a stroke of cosmic good fortune, 150 00:17:33,120 --> 00:17:35,320 the Earth has a satellite... 151 00:17:35,320 --> 00:17:40,080 ..the moon, which orbits our planet every 27 days. 152 00:17:43,560 --> 00:17:48,840 Its gravitational pull drags our oceans across the planet... 153 00:17:51,320 --> 00:17:53,680 ..and so gives us the tides. 154 00:17:58,960 --> 00:18:02,160 Unlike currents that stir the open ocean, 155 00:18:02,160 --> 00:18:05,280 the tides have their greatest impact on the coasts, 156 00:18:05,280 --> 00:18:09,840 flushing them with nutrients from both sea and land. 157 00:18:12,520 --> 00:18:16,040 And nowhere are they more violent and dramatic than here... 158 00:18:18,280 --> 00:18:21,160 ..Norway's Saltstraumen strait. 159 00:18:23,480 --> 00:18:25,120 Every six hours, 160 00:18:25,120 --> 00:18:27,520 nearly half a billion tonnes of water 161 00:18:27,520 --> 00:18:31,720 are forced through a channel just 150 metres wide. 162 00:18:33,800 --> 00:18:37,240 Its very narrowness accelerates the water... 163 00:18:38,680 --> 00:18:43,200 ..making this the strongest tidal pull in the world. 164 00:18:57,920 --> 00:19:00,720 Most animals caught here would be swept away. 165 00:19:04,200 --> 00:19:07,120 But not these tidal specialists. 166 00:19:07,120 --> 00:19:10,080 Eiders are one of the few ducks 167 00:19:10,080 --> 00:19:14,080 that depend totally on the ocean for their survival. 168 00:19:16,720 --> 00:19:19,360 And they're the only kind strong enough 169 00:19:19,360 --> 00:19:22,640 to live permanently in these racing waters. 170 00:19:30,160 --> 00:19:33,400 But there is food here, and in great quantity, 171 00:19:33,400 --> 00:19:35,000 for any that can gather it... 172 00:19:36,640 --> 00:19:38,040 ..mussels. 173 00:19:39,560 --> 00:19:44,880 They filter out particles of food brought to them by the tide. 174 00:19:46,040 --> 00:19:48,360 And eider ducks love mussels. 175 00:19:51,800 --> 00:19:53,880 The challenge is reaching them. 176 00:20:11,480 --> 00:20:13,800 Eiders seem to be the only creatures 177 00:20:13,800 --> 00:20:17,080 that can hold their own in the fast-flowing water... 178 00:20:20,000 --> 00:20:22,320 ..so they have the mussels all to themselves. 179 00:20:25,040 --> 00:20:28,080 They swallow them whole, shell and all. 180 00:20:32,160 --> 00:20:36,000 Each eider duck eats hundreds of mussels a day... 181 00:20:37,200 --> 00:20:40,840 ..a year-round feast that no others can reach. 182 00:20:52,400 --> 00:20:55,320 The tides here owe their power 183 00:20:55,320 --> 00:20:58,200 to the unique geography of the coastline. 184 00:20:59,400 --> 00:21:01,880 But, elsewhere in our oceans, 185 00:21:01,880 --> 00:21:06,360 the lay of the land influences tides in a very different way. 186 00:21:09,360 --> 00:21:11,320 Here in the Bahamas, 187 00:21:11,320 --> 00:21:15,640 wide, shallow sandbanks mean the tide moves gently 188 00:21:15,640 --> 00:21:18,400 over the sea floor... 189 00:21:18,400 --> 00:21:20,960 ..turning what would be a sandy desert 190 00:21:20,960 --> 00:21:23,400 into a rich underwater habitat. 191 00:21:27,000 --> 00:21:31,400 This is the home of garden eels and razorfish. 192 00:21:35,600 --> 00:21:40,360 And fresh food arrives for them from deeper waters twice a day. 193 00:21:43,240 --> 00:21:45,240 Life seems unhurried and gentle... 194 00:21:48,040 --> 00:21:51,000 ..but there is trouble in paradise. 195 00:21:54,080 --> 00:21:57,680 These bottlenose dolphins eat razorfish, 196 00:21:57,680 --> 00:22:00,880 and they're not so easily fooled by vanishing tricks. 197 00:22:06,600 --> 00:22:10,480 They scan the sand with echolocating clicks 198 00:22:10,480 --> 00:22:14,840 to discover exactly where the razorfish are hiding. 199 00:22:30,800 --> 00:22:34,120 But knowing where they are is not the same as catching them. 200 00:22:40,560 --> 00:22:43,080 The more the dolphins dig, 201 00:22:43,080 --> 00:22:45,120 the deeper the razorfish burrow. 202 00:22:48,720 --> 00:22:51,440 But it's clearly not deep enough. 203 00:23:01,000 --> 00:23:03,920 Blowing jets of water into the sand 204 00:23:03,920 --> 00:23:07,840 exposes even the most hard-to-reach razorfish. 205 00:23:11,480 --> 00:23:15,720 Before long, the dolphins have had enough and they move on. 206 00:23:18,040 --> 00:23:20,920 It looks as if they have picked the sand clean... 207 00:23:26,160 --> 00:23:28,120 ..but here, at least, 208 00:23:28,120 --> 00:23:31,160 there really are plenty more fish in the sea. 209 00:23:41,360 --> 00:23:45,200 Closer to the land, the same tides bring nourishment 210 00:23:45,200 --> 00:23:48,680 to one of the most threatened of coastal habitats... 211 00:23:49,680 --> 00:23:51,520 ..mangrove forests. 212 00:23:53,080 --> 00:23:55,240 Part land... 213 00:23:55,240 --> 00:23:56,960 ..part sea. 214 00:23:58,880 --> 00:24:01,720 Mangroves are the only trees 215 00:24:01,720 --> 00:24:04,800 capable of surviving in salt water 216 00:24:04,800 --> 00:24:09,080 and are specially adapted to it coming and going twice every day. 217 00:24:16,480 --> 00:24:19,960 As sea water floods in, fish come with it. 218 00:24:21,400 --> 00:24:23,480 Here in the flooded forests, 219 00:24:23,480 --> 00:24:26,920 they can find both food and shelter. 220 00:24:33,480 --> 00:24:36,880 Stingrays ride on the incoming tide. 221 00:24:44,280 --> 00:24:47,520 Other commuters follow. 222 00:24:47,520 --> 00:24:51,000 Young lemon sharks, still far from full-grown, 223 00:24:51,000 --> 00:24:52,880 are looking for food. 224 00:25:07,960 --> 00:25:10,320 When the tide is at its highest, 225 00:25:10,320 --> 00:25:12,520 even adult lemon sharks 226 00:25:12,520 --> 00:25:14,360 can get into the mangroves. 227 00:25:17,480 --> 00:25:21,440 A three-metre female moves cautiously into the shallows. 228 00:25:24,680 --> 00:25:27,040 She can't stay here for long, 229 00:25:27,040 --> 00:25:29,680 but, then, she hasn't come here to hunt. 230 00:25:36,080 --> 00:25:38,880 She's come to give birth... 231 00:25:40,320 --> 00:25:43,080 ..returning to the very place where she was born. 232 00:25:46,920 --> 00:25:50,360 She has nourished the pups inside her body 233 00:25:50,360 --> 00:25:52,680 with a placenta, as we do. 234 00:25:59,360 --> 00:26:02,920 The mangroves provide an ideal nursery for them, 235 00:26:02,920 --> 00:26:06,200 and placing them here gives them an excellent start, 236 00:26:06,200 --> 00:26:09,320 but that is the end of her parental care. 237 00:26:11,240 --> 00:26:15,360 She has to return to deeper water before the tide goes out. 238 00:26:19,720 --> 00:26:22,400 Her young must now fend for themselves. 239 00:26:26,040 --> 00:26:30,640 The pups instinctively take refuge among the roots of the mangroves. 240 00:26:33,720 --> 00:26:37,240 They're so small, they can swim deep 241 00:26:37,240 --> 00:26:39,160 into this tangled labyrinth. 242 00:26:50,600 --> 00:26:52,720 With the tide fast receding, 243 00:26:52,720 --> 00:26:54,720 even they need to find a place 244 00:26:54,720 --> 00:26:57,040 where they won't be left high and dry. 245 00:26:58,760 --> 00:27:00,560 A place like this... 246 00:27:01,840 --> 00:27:05,720 ..a permanent pool in the heart of the mangrove forest. 247 00:27:12,440 --> 00:27:15,240 Only the smallest sharks can get here, 248 00:27:15,240 --> 00:27:17,560 and only at the highest tides. 249 00:27:24,720 --> 00:27:27,640 The pups will spend the next two years here 250 00:27:27,640 --> 00:27:31,400 perfecting the skills that make them one of the ocean's top hunters. 251 00:27:36,320 --> 00:27:38,640 And it seems... 252 00:27:38,640 --> 00:27:40,560 ..that there's a lot to learn. 253 00:27:47,120 --> 00:27:48,520 Got one! 254 00:27:54,560 --> 00:27:59,240 All life at the coasts has to move to the daily rhythm of the tides, 255 00:28:00,480 --> 00:28:03,640 but tides are not the same throughout the year. 256 00:28:09,480 --> 00:28:15,320 Every month, when our planet, the moon and the sun are all aligned, 257 00:28:15,320 --> 00:28:17,960 the increased gravitational pull 258 00:28:17,960 --> 00:28:21,000 produces particularly high tides. 259 00:28:22,400 --> 00:28:26,040 And this triggers a truly extraordinary event 260 00:28:26,040 --> 00:28:28,680 on one particular reef in the central Pacific. 261 00:28:35,520 --> 00:28:38,400 Thousands of resident surgeonfish 262 00:28:38,400 --> 00:28:41,800 begin to assemble on these high tides. 263 00:28:46,320 --> 00:28:50,600 And they are being followed by one of the largest fish in the sea... 264 00:28:57,280 --> 00:28:59,120 ..manta rays. 265 00:29:08,520 --> 00:29:13,480 The rays spend their year moving between coral islands. 266 00:29:15,840 --> 00:29:20,040 But it's only now, when the tide is at its highest 267 00:29:20,040 --> 00:29:22,960 and the surgeonfish have gathered, that they appear 268 00:29:22,960 --> 00:29:25,000 on this particular reef. 269 00:29:28,640 --> 00:29:30,800 Their timing is so perfect 270 00:29:30,800 --> 00:29:33,680 that they rarely have to wait more than an hour 271 00:29:33,680 --> 00:29:35,480 for the event to begin. 272 00:30:01,920 --> 00:30:06,320 At the precise moment when the tide is at its highest, 273 00:30:06,320 --> 00:30:08,480 the surgeonfish begin to spawn. 274 00:30:11,160 --> 00:30:14,280 They release billions of eggs and sperm into the water. 275 00:30:19,400 --> 00:30:22,080 Breeding in this way gives their fertilised eggs 276 00:30:22,080 --> 00:30:25,320 the best chance of being carried on the tide 277 00:30:25,320 --> 00:30:27,880 away from predators that haunt the reef. 278 00:30:31,600 --> 00:30:33,200 All except one. 279 00:30:36,880 --> 00:30:38,880 The mantas move in. 280 00:30:56,600 --> 00:30:59,080 They gorge on the eggs, 281 00:30:59,080 --> 00:31:02,080 filtering them out using specially adapted gills. 282 00:31:04,440 --> 00:31:07,680 If the mantas had arrived just an hour later, 283 00:31:07,680 --> 00:31:10,240 there would have been nothing here for them to eat. 284 00:31:17,640 --> 00:31:21,360 No-one knows how the mantas are so perfectly in tune 285 00:31:21,360 --> 00:31:23,200 with the rhythm of the tides. 286 00:31:29,240 --> 00:31:33,520 But they appear without fail whenever the surgeonfish spawn. 287 00:31:41,840 --> 00:31:43,640 Most of the eggs, however, 288 00:31:43,640 --> 00:31:46,280 are carried out into the open ocean 289 00:31:46,280 --> 00:31:48,880 before the mantas are able to eat them all. 290 00:32:05,200 --> 00:32:11,040 The rhythms of coastal life are influenced by another ocean force. 291 00:32:14,760 --> 00:32:19,200 Winds blowing over the sea so batter the surface 292 00:32:19,200 --> 00:32:21,960 that it begins to rise and fall. 293 00:32:24,040 --> 00:32:25,880 These swells may travel far 294 00:32:25,880 --> 00:32:28,920 and reach the shores of even the most sheltered bays. 295 00:32:30,560 --> 00:32:32,880 As they approach shallower water, 296 00:32:32,880 --> 00:32:34,640 they turn into waves. 297 00:32:39,080 --> 00:32:41,640 A shoal of hardyheads, 298 00:32:41,640 --> 00:32:45,080 close to the beach of Australia's Lizard Island. 299 00:32:46,960 --> 00:32:51,960 The clearness of these glassy waters shows that they lack nutrients. 300 00:32:53,440 --> 00:32:57,400 But the gentle waves expose food hidden in the sand, 301 00:32:57,400 --> 00:32:59,960 and that's what the hardyheads are looking for. 302 00:33:10,040 --> 00:33:12,040 But...they must beware. 303 00:33:15,880 --> 00:33:18,440 Packs of trevally are on the hunt. 304 00:33:27,080 --> 00:33:29,480 The hardyheads stick together. 305 00:33:30,400 --> 00:33:32,160 There's safety in numbers. 306 00:33:33,640 --> 00:33:35,720 But they're vulnerable, nonetheless. 307 00:33:46,840 --> 00:33:49,880 They're so small, they can swim in the shallowest waters... 308 00:33:58,240 --> 00:34:01,520 ..even in the body of the waves themselves, 309 00:34:01,520 --> 00:34:03,760 out of the reach of their enemies. 310 00:34:08,880 --> 00:34:11,760 But trevally aren't their only concern. 311 00:34:21,200 --> 00:34:23,240 Blacktip reef sharks. 312 00:34:24,760 --> 00:34:28,760 They are bigger and more powerful than trevally... 313 00:34:30,640 --> 00:34:32,880 ..but not as fast or as agile. 314 00:34:37,960 --> 00:34:40,720 The hardyheads are well aware of them, 315 00:34:40,720 --> 00:34:43,360 but, so long as they stay just out of reach, 316 00:34:43,360 --> 00:34:44,880 they have little to fear. 317 00:34:59,240 --> 00:35:02,760 But now the sharks and the trevally join forces. 318 00:35:08,000 --> 00:35:10,760 Together, they enter the shallows, 319 00:35:10,760 --> 00:35:12,920 each looking for a chance to attack. 320 00:35:30,960 --> 00:35:32,840 The trevally make the first move... 321 00:35:34,600 --> 00:35:38,440 ..and the hardyheads take refuge again in the waves. 322 00:35:39,440 --> 00:35:41,920 And this is what the sharks have been waiting for. 323 00:35:46,400 --> 00:35:50,600 Surging forwards, they chase the hardyheads out of the water... 324 00:35:51,640 --> 00:35:55,880 ..beaching themselves in a daring bid to hoover up their prey. 325 00:36:00,360 --> 00:36:02,840 The hardyheads that escape the sharks 326 00:36:02,840 --> 00:36:04,720 swim back out to deeper water... 327 00:36:06,840 --> 00:36:09,200 ..but into the mouths of the trevally. 328 00:36:20,320 --> 00:36:23,760 Now the receding waves help to pull the sharks back 329 00:36:23,760 --> 00:36:25,600 into deeper water. 330 00:36:56,200 --> 00:36:59,760 In the chaos, the sea birds get their chance. 331 00:37:04,720 --> 00:37:07,280 It's a feeding frenzy... 332 00:37:07,280 --> 00:37:09,840 ..in only ten centimetres of water. 333 00:37:22,760 --> 00:37:26,840 The power of waves is dramatically evident 334 00:37:26,840 --> 00:37:28,480 when they crash onto our shores. 335 00:37:31,840 --> 00:37:37,360 But the biggest of all start far away from land, out at sea. 336 00:37:39,760 --> 00:37:43,680 Great storms blowing over the surface of the ocean 337 00:37:43,680 --> 00:37:46,280 raise towering walls of water. 338 00:37:49,800 --> 00:37:53,920 Such giant swells can travel for thousands of miles. 339 00:37:56,480 --> 00:37:58,480 As they approach land, 340 00:37:58,480 --> 00:38:03,200 the shallowing sea floor begins to drag on their undersides, 341 00:38:03,200 --> 00:38:05,320 and they topple forward... 342 00:38:05,320 --> 00:38:06,760 ..and break. 343 00:38:10,560 --> 00:38:14,840 This stirring of the ocean produces great riches. 344 00:38:18,640 --> 00:38:20,720 The Falkland Islands are surrounded 345 00:38:20,720 --> 00:38:22,920 by some of the stormiest waters on Earth... 346 00:38:27,040 --> 00:38:31,600 ..ideal hunting grounds for rockhopper penguins. 347 00:38:33,320 --> 00:38:35,320 It's the breeding season 348 00:38:35,320 --> 00:38:37,000 and, for the last two weeks, 349 00:38:37,000 --> 00:38:39,800 the males have been incubating the eggs by themselves. 350 00:38:42,680 --> 00:38:45,640 They're confined to the nest with nothing to eat, 351 00:38:45,640 --> 00:38:48,280 while the females are out at sea collecting food. 352 00:38:53,000 --> 00:38:57,000 All across the colony, eggs are starting to hatch. 353 00:38:58,960 --> 00:39:02,520 This male now has two youngsters to care for. 354 00:39:05,840 --> 00:39:10,040 But he has no food to give them, and he can't leave them unprotected. 355 00:39:11,760 --> 00:39:14,160 He can do nothing but wait. 356 00:39:24,240 --> 00:39:28,160 The females, after weeks fishing in the stormy seas, 357 00:39:28,160 --> 00:39:31,720 are now heading for home with food in their crops. 358 00:39:35,760 --> 00:39:37,280 There's just one problem. 359 00:39:38,600 --> 00:39:41,640 The colony sits at the top of huge cliffs. 360 00:39:44,680 --> 00:39:48,120 The waves that make feeding so good here 361 00:39:48,120 --> 00:39:51,160 have now become major obstacles. 362 00:39:53,360 --> 00:39:55,440 Timing is vital. 363 00:40:09,640 --> 00:40:11,240 Go too early... 364 00:40:12,240 --> 00:40:14,800 ..and they could be smashed against the rocks. 365 00:40:21,080 --> 00:40:23,880 Too late... 366 00:40:23,880 --> 00:40:26,120 ..and they will be carried back out to sea. 367 00:40:32,360 --> 00:40:34,720 Hooked claws now help to get purchase 368 00:40:34,720 --> 00:40:36,440 on the slippery rocks. 369 00:40:39,920 --> 00:40:41,680 But they're not out of trouble yet. 370 00:40:46,720 --> 00:40:49,800 Success depends on both judgment... 371 00:40:49,800 --> 00:40:51,280 ..and luck. 372 00:41:11,280 --> 00:41:15,240 Time and again, the waves drag her back in. 373 00:41:21,560 --> 00:41:23,520 She has to persevere. 374 00:41:23,520 --> 00:41:28,120 The lives of her chicks depend on her safe return. 375 00:42:00,040 --> 00:42:02,120 Finally... 376 00:42:02,120 --> 00:42:04,200 ..she's made it. 377 00:42:13,520 --> 00:42:16,280 They're not called rockhoppers for nothing. 378 00:42:21,960 --> 00:42:24,200 With one more jump, she's home. 379 00:42:27,680 --> 00:42:29,400 And just in time. 380 00:42:34,560 --> 00:42:36,840 Her chicks are desperately hungry. 381 00:42:44,680 --> 00:42:47,760 This is their first proper meal. 382 00:42:57,640 --> 00:43:01,960 The oceans have sustained life on our planet for millions of years. 383 00:43:06,720 --> 00:43:11,280 But, today, there's growing evidence that this is changing. 384 00:43:17,320 --> 00:43:19,360 As our climate warms, 385 00:43:19,360 --> 00:43:22,880 polar ice sheets are melting at an alarming rate. 386 00:43:26,920 --> 00:43:31,360 In the Arctic alone, 14,000 tonnes of fresh water 387 00:43:31,360 --> 00:43:34,560 are emptying into the sea every second. 388 00:43:42,440 --> 00:43:45,960 This is slowing the flow of currents around the globe. 389 00:43:48,840 --> 00:43:51,920 And, if the atmosphere continues to warm, 390 00:43:51,920 --> 00:43:55,760 ocean circulation could eventually stop altogether. 391 00:44:04,720 --> 00:44:07,880 Our seas would then stagnate, 392 00:44:07,880 --> 00:44:10,640 threatening the life within them. 393 00:44:14,360 --> 00:44:16,960 And there are places in the oceans today 394 00:44:16,960 --> 00:44:19,840 where this is already beginning to happen. 395 00:44:28,640 --> 00:44:30,520 The Gulf of Thailand. 396 00:44:37,680 --> 00:44:40,800 Eden's whales have lived here for generations. 397 00:44:44,320 --> 00:44:46,840 But the world around them is changing. 398 00:44:56,120 --> 00:44:59,800 Today, agricultural pollution flowing from the land... 399 00:45:02,480 --> 00:45:05,320 ..is beginning to suffocate this sea. 400 00:45:15,480 --> 00:45:18,760 Many fish now stay closer to the surface, 401 00:45:18,760 --> 00:45:22,600 where the waters still contain enough oxygen to survive. 402 00:45:27,200 --> 00:45:30,520 Eden's whales depend on these fish. 403 00:45:32,520 --> 00:45:35,120 They swallow huge quantities of water 404 00:45:35,120 --> 00:45:37,200 before filtering out their prey. 405 00:45:42,520 --> 00:45:46,520 It takes a lot of energy to drive their 15-tonne bulk 406 00:45:46,520 --> 00:45:48,400 through the water. 407 00:45:51,200 --> 00:45:53,480 And, with so few fish, 408 00:45:53,480 --> 00:45:56,440 the rewards from feeding like this are barely worth it. 409 00:45:59,040 --> 00:46:01,480 So, to survive here, 410 00:46:01,480 --> 00:46:04,720 the whales have developed a new hunting technique... 411 00:46:09,400 --> 00:46:12,680 ..one that requires almost no effort. 412 00:46:15,760 --> 00:46:18,640 They simply open their mouths... 413 00:46:18,640 --> 00:46:20,040 ..and wait. 414 00:46:25,400 --> 00:46:27,880 The panicked fish jump right in. 415 00:46:35,360 --> 00:46:37,240 Swimming alongside, 416 00:46:37,240 --> 00:46:40,760 another whale scares even more into the open jaws. 417 00:46:52,800 --> 00:46:55,560 With this ingenious new technique, 418 00:46:55,560 --> 00:46:59,400 Eden's whales have found a way to survive the pressures 419 00:46:59,400 --> 00:47:00,760 they now face. 420 00:47:03,240 --> 00:47:07,240 All across the planet, animals are having to adapt 421 00:47:07,240 --> 00:47:09,120 to a changing world. 422 00:47:10,960 --> 00:47:14,600 But the speed of these changes will be too fast for many. 423 00:47:19,960 --> 00:47:25,240 If we could only halt our unrestrained plunder of the ocean, 424 00:47:25,240 --> 00:47:27,920 its habitats and species would recover. 425 00:47:30,800 --> 00:47:33,480 And, at a time when our overexploited lands 426 00:47:33,480 --> 00:47:35,640 are already failing us, 427 00:47:35,640 --> 00:47:38,680 this has never been more important for humanity. 428 00:47:59,560 --> 00:48:03,320 The volcanic island of Fernandina in the Galapagos 429 00:48:03,320 --> 00:48:06,080 is home to two incredible lizards... 430 00:48:08,280 --> 00:48:12,640 ..the land iguana and the marine iguana. 431 00:48:14,480 --> 00:48:17,160 There are two parts to their story 432 00:48:17,160 --> 00:48:19,840 that cameraman, Richard Wollocombe, has wanted to film 433 00:48:19,840 --> 00:48:23,600 since he first came to these islands 25 years ago, 434 00:48:24,800 --> 00:48:27,880 and, on A Perfect Planet, he got his chance. 435 00:48:32,640 --> 00:48:34,760 Driven by powerful currents, 436 00:48:34,760 --> 00:48:39,160 the cold Pacific Ocean slams into Fernandina's shores. 437 00:48:45,720 --> 00:48:49,200 The marine iguanas must brave these waters every day. 438 00:48:54,000 --> 00:48:57,120 Their journey through the big surf is what Richard and the team 439 00:48:57,120 --> 00:48:59,280 are here to film... 440 00:48:59,280 --> 00:49:01,200 ..but from underwater. 441 00:49:02,200 --> 00:49:04,520 It looks fairly benign from the surface here, 442 00:49:04,520 --> 00:49:07,240 but, underneath, it's really shallow, 443 00:49:07,240 --> 00:49:11,200 and there's all these really sharp rocks with lots of jagged edges. 444 00:49:11,200 --> 00:49:13,600 So if we were taken by the wave, 445 00:49:13,600 --> 00:49:16,440 it would cut us up really badly, I think. 446 00:49:21,120 --> 00:49:23,000 Whose idea was this? 447 00:49:23,000 --> 00:49:24,680 Ha-ha, ha-ha. 448 00:49:25,800 --> 00:49:28,000 I'm a glutton for punishment, did you know? 449 00:49:31,920 --> 00:49:35,000 The waves are certainly punishing. 450 00:49:35,960 --> 00:49:38,240 With these dangerous conditions, 451 00:49:38,240 --> 00:49:42,400 extra protection is clearly needed for Richard and dive buddy Rafael. 452 00:49:43,360 --> 00:49:46,040 So what better than surf helmets? 453 00:49:54,440 --> 00:49:58,760 It isn't long before Richard realises what he's up against. 454 00:50:01,760 --> 00:50:04,760 The relentless churning of the water makes it difficult 455 00:50:04,760 --> 00:50:07,240 to stay the right way up... 456 00:50:07,240 --> 00:50:08,840 ..let alone film the iguanas. 457 00:50:14,440 --> 00:50:18,200 In between the waves, the iguanas briefly appear. 458 00:50:22,880 --> 00:50:25,800 But Richard barely has time to line up a shot... 459 00:50:26,760 --> 00:50:29,960 ..before the iguana disappears behind another wave. 460 00:50:37,480 --> 00:50:39,000 In the violent surge, 461 00:50:39,000 --> 00:50:41,960 the iguanas have learned to hang on to the rocks... 462 00:50:43,360 --> 00:50:47,640 ..a trick Richard is quick to copy to avoid being swept away. 463 00:50:49,440 --> 00:50:52,440 That, however, only leaves one hand to film with. 464 00:51:01,400 --> 00:51:04,240 But, with adrenaline carrying him through, 465 00:51:04,240 --> 00:51:08,240 Richard is able to get the perfect shots of iguanas in the surf. 466 00:51:14,520 --> 00:51:19,120 And to achieve that totally unscathed is a great relief. 467 00:51:20,080 --> 00:51:22,800 I don't need to go to the gym for months after that! 468 00:51:25,120 --> 00:51:27,360 Well done, mate. Good job. 469 00:51:30,400 --> 00:51:35,400 On the shore, land iguanas have to battle a very different force. 470 00:51:37,920 --> 00:51:43,520 Each year, they migrate up to the top of Fernandina's active volcano, 471 00:51:43,520 --> 00:51:47,840 a journey of ten days across razor-sharp lava 472 00:51:47,840 --> 00:51:50,960 before descending into its heart to lay their eggs 473 00:51:50,960 --> 00:51:52,800 in the ashy floor. 474 00:51:57,640 --> 00:52:02,000 It's this behaviour Richard and the team plan to film, 475 00:52:02,000 --> 00:52:05,840 and the scale of the expedition is one that's rarely been attempted 476 00:52:05,840 --> 00:52:07,680 in the Galapagos. 477 00:52:12,280 --> 00:52:16,640 To reach the top takes the crew ten gruelling hours. 478 00:52:26,520 --> 00:52:28,960 When they finally arrive on the rim, 479 00:52:28,960 --> 00:52:31,040 the experience doesn't disappoint. 480 00:52:33,320 --> 00:52:35,240 I can't believe it. 481 00:52:35,240 --> 00:52:37,880 It's absolutely awe-inspiring. 482 00:52:40,000 --> 00:52:43,160 I just can't believe the iguanas actually manage 483 00:52:43,160 --> 00:52:47,800 to navigate down these slopes into the bowl of this volcano. 484 00:52:49,480 --> 00:52:52,640 More people have been into space than to the bottom 485 00:52:52,640 --> 00:52:54,800 of Fernandina's crater. 486 00:52:54,800 --> 00:52:58,240 But that is exactly where Richard and the team must go 487 00:52:58,240 --> 00:53:00,880 if they are to film the nesting iguanas. 488 00:53:05,680 --> 00:53:08,640 From their campsite at the edge of the volcano, 489 00:53:08,640 --> 00:53:12,040 it's an extremely dangerous journey down to the crater floor, 490 00:53:12,040 --> 00:53:16,520 and assistant producer Toby wants to be clear with everyone 491 00:53:16,520 --> 00:53:18,440 what is at stake. 492 00:53:36,320 --> 00:53:39,680 There's only one passable route down, 493 00:53:39,680 --> 00:53:43,680 and, as the team enter the lip of the volcano, 494 00:53:43,680 --> 00:53:46,760 the sound of rock fall is all around. 495 00:53:55,640 --> 00:53:59,680 Regular earthquakes make the crater walls very unstable. 496 00:54:04,720 --> 00:54:07,080 Just keeps getting better. 497 00:54:07,080 --> 00:54:11,320 Not far away, some iguanas are making their own descent, 498 00:54:11,320 --> 00:54:13,840 disturbing the loose surface as they go. 499 00:54:25,360 --> 00:54:28,560 If a creature only a sixth the size of a person 500 00:54:28,560 --> 00:54:32,200 can start a deadly avalanche of razor-sharp rocks, 501 00:54:32,200 --> 00:54:34,800 what can a whole film crew do? 502 00:54:41,360 --> 00:54:45,920 It's clear the crew are going to have to be extremely cautious. 503 00:54:50,640 --> 00:54:53,400 On the steepest slopes, the equipment needs to be 504 00:54:53,400 --> 00:54:55,000 lowered with ropes. 505 00:55:03,200 --> 00:55:07,200 With rocks falling all around, the longer they're on the slopes, 506 00:55:07,200 --> 00:55:09,800 the greater the risk of an accident. 507 00:55:13,960 --> 00:55:16,880 But, when one misstep can start an avalanche, 508 00:55:16,880 --> 00:55:18,560 hurrying is impossible. 509 00:55:21,720 --> 00:55:25,400 Finally, the prize of the crater floor is in sight. 510 00:55:25,400 --> 00:55:29,080 Look, just below there is where the iguanas are nesting. 511 00:55:29,080 --> 00:55:33,000 We're very close to it now, about an hour's walk. 512 00:55:33,000 --> 00:55:36,640 All that lies between them is a stretch of loose lava 513 00:55:36,640 --> 00:55:39,960 that has cascaded down the slopes after the last eruption. 514 00:55:53,720 --> 00:55:56,240 We're actually in the crater now, 515 00:55:56,240 --> 00:55:58,960 surrounded by these vertical walls. 516 00:56:00,720 --> 00:56:04,080 I just can't believe that we really made it down here. 517 00:56:05,040 --> 00:56:08,840 Sometimes I doubted that, you know, we would actually make it. 518 00:56:12,080 --> 00:56:16,280 And there they were, iguanas, using the warm volcanic ash 519 00:56:16,280 --> 00:56:18,240 to incubate their eggs. 520 00:56:22,840 --> 00:56:27,760 For Richard, after 25 years living in the Galapagos, 521 00:56:27,760 --> 00:56:31,920 filming this unique behaviour is a lifelong dream come true. 522 00:56:34,280 --> 00:56:37,400 My, God, what an incredible place this is! 523 00:56:37,400 --> 00:56:42,080 It's such a vivid feeling to be constantly challenged 524 00:56:42,080 --> 00:56:44,040 by the forces of nature like that. 525 00:56:45,280 --> 00:56:49,160 But they have to do this every year in order to survive. 526 00:56:49,160 --> 00:56:52,760 I'll never forget, for as long as I live. 527 00:56:52,760 --> 00:56:55,000 What an adventure! What an adventure! 528 00:56:59,200 --> 00:57:00,920 Next time... 529 00:57:00,920 --> 00:57:02,800 ..a new force... 530 00:57:02,800 --> 00:57:04,520 ..humans. 531 00:57:04,520 --> 00:57:06,280 Now so dominant... 532 00:57:07,320 --> 00:57:09,520 ..we're disrupting the forces of nature... 533 00:57:11,480 --> 00:57:15,520 ..and the vital habitats life needs to survive. 534 00:57:17,000 --> 00:57:19,840 This is the most important story... 535 00:57:19,840 --> 00:57:21,760 ..of our time. 536 00:57:21,760 --> 00:57:23,800 Whose future? Our future.