1 00:00:43,200 --> 00:00:48,040 Much of our planet still remains unexplored... 2 00:00:50,720 --> 00:00:53,960 ..for most of it is covered by water. 3 00:00:56,600 --> 00:01:01,440 Every journey below the surface can reveal something extraordinary. 4 00:01:04,840 --> 00:01:10,560 More than a thousand new species are discovered here every year. 5 00:01:24,760 --> 00:01:32,760 The ocean is home to 80% of all animal life on Planet Earth. 6 00:01:40,480 --> 00:01:45,680 But today, thriving in this varied world 7 00:01:45,680 --> 00:01:50,520 sometimes demands the most surprising behaviour. 8 00:02:11,520 --> 00:02:14,960 The shallow seas of the tropics. 9 00:02:17,760 --> 00:02:21,120 This may look like a paradise... 10 00:02:24,120 --> 00:02:28,560 ..but beneath the surface, it is an arena 11 00:02:28,560 --> 00:02:31,960 for constant life-and-death struggles, 12 00:02:31,960 --> 00:02:35,520 where not everything is quite as it seems. 13 00:02:45,080 --> 00:02:48,680 A predatory lionfish... 14 00:02:51,440 --> 00:02:54,760 ..on the hunt for shrimp and small fish. 15 00:03:03,600 --> 00:03:07,920 With so many places for its prey to hide, 16 00:03:07,920 --> 00:03:10,920 the lionfish has to be patient. 17 00:03:17,720 --> 00:03:21,080 This shrimp appears tempting. 18 00:03:22,680 --> 00:03:25,160 As the lion-fish closes in, 19 00:03:25,160 --> 00:03:30,000 it fans out its fins to disorientate its prey. 20 00:03:42,640 --> 00:03:45,560 The hunter becomes the hunted. 21 00:03:52,000 --> 00:03:54,560 Tricked by one of the shallow sea's 22 00:03:54,560 --> 00:03:57,120 most extraordinary predators... 23 00:04:01,120 --> 00:04:03,880 ..a clown frogfish! 24 00:04:06,400 --> 00:04:10,000 On its head, it carries a fishing rod – 25 00:04:10,000 --> 00:04:12,320 a modified dorsal fin, 26 00:04:12,320 --> 00:04:17,240 baited with a lure - easily mistaken for a shrimp. 27 00:04:27,680 --> 00:04:30,400 But, when the fish stop biting, 28 00:04:30,400 --> 00:04:33,000 it's time to pack the rod away 29 00:04:33,000 --> 00:04:35,280 and move on. 30 00:04:38,280 --> 00:04:43,920 And, for a frogfish, that takes time. 31 00:04:54,640 --> 00:04:59,080 Rather than swim, frogfish walk! 32 00:05:01,000 --> 00:05:04,760 Its fins have, in effect, become feet. 33 00:05:14,320 --> 00:05:16,360 It may not look pretty, 34 00:05:16,360 --> 00:05:23,000 but what appears to be coral living on its skin is actually camouflage. 35 00:05:36,640 --> 00:05:39,320 As every good angler knows, 36 00:05:39,320 --> 00:05:42,440 picking the right spot is important. 37 00:05:47,800 --> 00:05:51,280 Jigging the rod sends out pressure waves 38 00:05:51,280 --> 00:05:54,520 to attract the attention of possible prey. 39 00:06:02,680 --> 00:06:05,840 These dragonets are certainly interested. 40 00:06:18,480 --> 00:06:20,880 Almost there. 41 00:06:34,920 --> 00:06:37,640 Hook, line, and sinker. 42 00:06:49,680 --> 00:06:52,880 Like all shallow seas, the cold waters 43 00:06:52,880 --> 00:06:55,840 off the coast of North America, 44 00:06:55,840 --> 00:06:59,560 benefit from the intensity of the sunshine. 45 00:07:06,680 --> 00:07:08,640 Here, that fuels 46 00:07:08,640 --> 00:07:12,160 one of the fastest-growing organisms on the planet... 47 00:07:14,160 --> 00:07:16,120 ..giant kelp. 48 00:07:18,840 --> 00:07:22,640 Towering forests can eventually reach the height 49 00:07:22,640 --> 00:07:25,080 of a 12-storey building. 50 00:07:38,000 --> 00:07:43,040 These forests are nurseries for young horn sharks. 51 00:07:46,560 --> 00:07:48,720 As the sun begins to set, 52 00:07:48,720 --> 00:07:51,840 they leave their daytime shelter 53 00:07:51,840 --> 00:07:57,440 and set off into the heart of the kelp forest to find food. 54 00:08:07,680 --> 00:08:09,640 Barely half a metre long, 55 00:08:09,640 --> 00:08:13,440 this little shark is extremely vulnerable. 56 00:08:20,200 --> 00:08:23,280 There are monsters here. 57 00:08:23,280 --> 00:08:26,080 A giant sea bass – 58 00:08:26,080 --> 00:08:29,040 weighing over 200kg... 59 00:08:32,280 --> 00:08:35,880 ..and wolf-eels, with big teeth 60 00:08:35,880 --> 00:08:39,200 that can crush little red sea urchins. 61 00:08:41,520 --> 00:08:45,200 But the biggest danger comes from other sharks - 62 00:08:49,400 --> 00:08:52,560 houndsharks... 63 00:08:56,160 --> 00:08:59,880 ..and huge broadnose sevengills. 64 00:09:11,520 --> 00:09:16,120 In this forest, it pays to keep a low profile. 65 00:09:49,600 --> 00:09:52,040 An angel shark... 66 00:09:55,400 --> 00:09:59,440 ..one of the most deadly sharks in the kelp forest, 67 00:09:59,440 --> 00:10:03,040 and certainly the best camouflaged. 68 00:10:13,640 --> 00:10:18,520 An angel shark will lie in wait for days... 69 00:10:27,960 --> 00:10:33,800 ..but this one has already attracted too much attention. 70 00:10:40,400 --> 00:10:43,040 It's not welcome here. 71 00:10:49,840 --> 00:10:52,400 Now, the coast is clear. 72 00:11:00,360 --> 00:11:04,080 But angel sharks hunt around the clock. 73 00:11:14,240 --> 00:11:18,080 Openings for breathing, called spiracles, 74 00:11:18,080 --> 00:11:21,400 blow out sand that helps cover its body. 75 00:11:28,680 --> 00:11:31,480 The trap is set. 76 00:11:42,920 --> 00:11:49,040 Staying close to the seabed is a good way to avoid most predators. 77 00:12:38,520 --> 00:12:42,000 Faster than the blink of an eye. 78 00:12:45,320 --> 00:12:47,840 But it's not over yet. 79 00:12:59,840 --> 00:13:03,880 Horn sharks have a secret weapon. 80 00:13:08,640 --> 00:13:12,880 Sharp spikes keep them very much off the menu for most. 81 00:13:19,400 --> 00:13:25,200 So, this young horn shark can hunt in safety... 82 00:13:27,160 --> 00:13:29,160 ..for now. 83 00:13:55,760 --> 00:14:00,720 Violent winter storms batter these kelp forests. 84 00:14:08,000 --> 00:14:11,160 The plants can be ripped from the seafloor... 85 00:14:14,120 --> 00:14:17,720 ..and carried away far out to sea. 86 00:14:29,680 --> 00:14:34,960 The open ocean is a vast, featureless desert. 87 00:14:38,840 --> 00:14:43,560 Even a small piece of drifting kelp can become valuable. 88 00:14:53,520 --> 00:14:58,520 It's just what these fish have been searching for. 89 00:15:00,280 --> 00:15:05,400 Here, shelter where eggs can be laid unobtrusively is rare... 90 00:15:07,200 --> 00:15:09,960 ..so they make the most of it. 91 00:15:11,920 --> 00:15:16,120 Each female produces up to a thousand eggs, 92 00:15:16,120 --> 00:15:19,440 and the males rush in to fertilise them. 93 00:15:30,040 --> 00:15:35,360 All this activity attracts the attention of blue sharks. 94 00:15:38,280 --> 00:15:40,920 They can travel thousands of miles 95 00:15:40,920 --> 00:15:43,560 through the ocean in search of food... 96 00:15:47,960 --> 00:15:52,920 ..and they may not have eaten for weeks. 97 00:15:52,920 --> 00:15:55,680 It seems that they're in luck. 98 00:16:03,640 --> 00:16:07,600 But these fish are no easy meal. 99 00:16:13,560 --> 00:16:16,040 They are flying fish! 100 00:17:15,120 --> 00:17:17,920 The blue shark, however, 101 00:17:17,920 --> 00:17:20,040 are not here for the fish... 102 00:17:23,040 --> 00:17:27,160 ..they have come for the caviar. 103 00:17:41,840 --> 00:17:44,720 But flying fish lay so many eggs, 104 00:17:44,720 --> 00:17:48,160 that the sharks' feasts hardly make an impact. 105 00:17:56,480 --> 00:18:01,960 And, in a few months' time, a new generation will take to the skies. 106 00:18:15,120 --> 00:18:20,040 Floating islands of weed are always attractive to creatures 107 00:18:20,040 --> 00:18:23,520 looking for shelter out in the big blue. 108 00:18:25,120 --> 00:18:29,600 But, in today's ocean, they are being replaced by something else... 109 00:18:35,000 --> 00:18:36,800 ..plastic. 110 00:18:38,800 --> 00:18:43,440 12 million tons of it end up in the ocean every year. 111 00:18:46,840 --> 00:18:52,360 The deadliest kind are discarded fishing lines and nets. 112 00:18:56,000 --> 00:19:00,800 Each year, it's likely over half a million animals are ensnared 113 00:19:00,800 --> 00:19:04,480 and killed by these "ghost nets." 114 00:19:14,040 --> 00:19:16,400 But some animals are learning 115 00:19:16,400 --> 00:19:19,520 how to take advantage of the plastic rafts... 116 00:19:22,320 --> 00:19:26,920 ..and use them for shelter, or even as a home. 117 00:19:29,840 --> 00:19:34,960 This male Columbus crab – barely bigger than your thumb nail – 118 00:19:34,960 --> 00:19:37,360 is a castaway. 119 00:19:40,440 --> 00:19:42,040 Clinging to his net, 120 00:19:42,040 --> 00:19:46,080 he may have been drifting on ocean currents for months. 121 00:19:49,040 --> 00:19:53,040 Now, fully grown, he needs to find a partner. 122 00:19:55,400 --> 00:19:57,600 But where? 123 00:20:05,160 --> 00:20:07,640 Certainly not here, 124 00:20:07,640 --> 00:20:10,400 alone on the net. 125 00:20:19,160 --> 00:20:24,520 Columbus crabs are not good swimmers, so this male is marooned. 126 00:20:34,360 --> 00:20:37,920 Perhaps a passing loggerhead turtle could be the chance 127 00:20:37,920 --> 00:20:39,640 to hitch a lift. 128 00:21:30,720 --> 00:21:32,160 Made it! 129 00:21:35,040 --> 00:21:39,360 But there's more than one passenger here - 130 00:21:39,360 --> 00:21:42,360 a female Columbus crab! 131 00:21:50,120 --> 00:21:53,760 They waste no time in getting acquainted... 132 00:21:57,160 --> 00:21:59,560 ..and start to mate. 133 00:22:07,280 --> 00:22:12,040 This pair may well stay together for the rest of their lives. 134 00:22:21,880 --> 00:22:26,560 A turtle, after all, makes an excellent home. 135 00:22:34,840 --> 00:22:40,000 In return, the crabs provide an onboard grooming service. 136 00:23:10,840 --> 00:23:16,240 Finding a partner in the vast ocean is not easy. 137 00:23:22,840 --> 00:23:26,720 Dawn in the Sea of Cortez... 138 00:23:50,160 --> 00:23:52,640 ..Mobula rays. 139 00:24:12,800 --> 00:24:16,640 They're gathering here, most likely to breed. 140 00:24:21,600 --> 00:24:24,560 No-one is sure why they leap, 141 00:24:24,560 --> 00:24:29,160 but the loud splashes certainly seem to attract more rays. 142 00:24:33,320 --> 00:24:37,600 Other creatures, however, are also listening. 143 00:24:48,040 --> 00:24:51,360 Orca have heard the splashes. 144 00:25:12,840 --> 00:25:17,200 This female specialises in hunting rays. 145 00:25:24,400 --> 00:25:28,240 But today, she is teaching two youngsters 146 00:25:28,240 --> 00:25:32,560 the finer points of Mobula ray hunting. 147 00:25:44,240 --> 00:25:48,680 The rays are fast and can outmanoeuvre an orca. 148 00:25:56,880 --> 00:26:01,720 She knows she needs to herd the prey into a tight group... 149 00:26:06,680 --> 00:26:10,200 ..but she can't do that on her own. 150 00:26:10,200 --> 00:26:14,160 It will take teamwork, 151 00:26:14,160 --> 00:26:16,840 and that is today's lesson. 152 00:26:24,160 --> 00:26:28,200 The young orca are quick to catch on. 153 00:26:32,760 --> 00:26:36,040 The rays are surrounded. 154 00:26:39,840 --> 00:26:42,160 They dive... 155 00:26:45,000 --> 00:26:50,200 ..only to be forced back up again by the experienced female. 156 00:26:53,880 --> 00:26:59,280 And now, with the exhausted rays trapped against the surface, 157 00:26:59,280 --> 00:27:01,600 she attacks... 158 00:27:14,640 --> 00:27:18,560 ..and the young ones follow her lead. 159 00:27:27,600 --> 00:27:32,360 This family are the only orca known to hunt rays like this... 160 00:27:33,960 --> 00:27:36,920 ..and they are lethally efficient. 161 00:27:41,800 --> 00:27:46,200 But it appears that school is over for today. 162 00:27:48,200 --> 00:27:50,880 For a few battle-scarred survivors, 163 00:27:50,880 --> 00:27:53,360 it's a lucky reprieve. 164 00:28:03,880 --> 00:28:08,800 With the orca gone, the rays can resume their courtship... 165 00:28:17,040 --> 00:28:20,960 ..and they do so in astounding numbers. 166 00:28:30,120 --> 00:28:34,320 Tens of thousands of rays in a single shoal. 167 00:28:49,640 --> 00:28:53,640 Vast areas of our ocean are yet to be explored. 168 00:28:55,600 --> 00:28:59,960 The least known parts of it are its great depths. 169 00:29:06,480 --> 00:29:10,800 Only highly-specialised vessels can take you there. 170 00:29:16,080 --> 00:29:20,520 As you descend, the sunlight rapidly fades. 171 00:29:26,840 --> 00:29:31,600 200m down, you enter the twilight zone... 172 00:29:38,800 --> 00:29:45,040 ..an alien world, inhabited by creatures beyond imagination. 173 00:30:06,720 --> 00:30:12,680 A siphonophore – with a cloak of lethal stinging tentacles. 174 00:30:25,760 --> 00:30:29,840 Siphonophores repeatedly clone themselves 175 00:30:29,840 --> 00:30:32,920 and so grow to immense lengths. 176 00:30:37,440 --> 00:30:43,320 This one measures 45m and is the longest animal ever recorded. 177 00:30:48,080 --> 00:30:50,320 With such deadly predators around, 178 00:30:50,320 --> 00:30:54,080 creatures here go to great lengths to hide. 179 00:31:04,680 --> 00:31:07,120 A glass squid... 180 00:31:08,840 --> 00:31:11,640 ..completely transparent, 181 00:31:11,640 --> 00:31:14,200 except for its eyes... 182 00:31:17,720 --> 00:31:21,000 ..and stomach, 183 00:31:21,000 --> 00:31:24,920 so it is extremely difficult to find in the gloom. 184 00:31:46,040 --> 00:31:48,920 Below 1,000m, 185 00:31:48,920 --> 00:31:52,680 all traces of sunlight have disappeared. 186 00:31:54,840 --> 00:31:58,480 This is the midnight zone. 187 00:32:03,680 --> 00:32:08,320 Catching food in the perpetual darkness is not easy. 188 00:32:29,240 --> 00:32:31,640 A gulper eel. 189 00:32:39,720 --> 00:32:41,920 Its giant, extendable mouth 190 00:32:41,920 --> 00:32:45,400 can engulf prey larger than its own body. 191 00:33:08,880 --> 00:33:14,000 Two miles down, you finally reach the ocean floor. 192 00:33:19,560 --> 00:33:23,080 We know more about the surface of Mars. 193 00:33:28,480 --> 00:33:34,600 The pressure of the water is 300 times greater than at the surface... 194 00:33:34,600 --> 00:33:37,040 ..and it's freezing cold. 195 00:33:39,360 --> 00:33:44,360 Yet, amazingly, there are animals living here. 196 00:33:49,720 --> 00:33:52,640 Muusoctopus robustus, 197 00:33:52,640 --> 00:33:55,920 nicknamed the pearl octopus. 198 00:33:58,880 --> 00:34:02,560 Breeding, in these extreme conditions poses 199 00:34:02,560 --> 00:34:05,600 a particular problem for these animals. 200 00:34:08,680 --> 00:34:11,000 At these low temperatures, 201 00:34:11,000 --> 00:34:15,640 this female's eggs could take over ten years to develop. 202 00:34:24,760 --> 00:34:29,040 So she travels to a very special place. 203 00:34:43,200 --> 00:34:48,600 This is the largest known gathering of octopus in the world. 204 00:34:58,480 --> 00:35:02,520 She joins 20,000 other females... 205 00:35:04,440 --> 00:35:07,320 ..all here to lay their eggs. 206 00:35:13,800 --> 00:35:17,400 Water, heated deep in the Earth's crust, 207 00:35:17,400 --> 00:35:20,680 rises through cracks in the seabed... 208 00:35:22,560 --> 00:35:27,840 ..raising the temperature to as much as 10 degrees Celsius. 209 00:35:29,240 --> 00:35:32,080 A deep-sea thermal spa! 210 00:35:37,080 --> 00:35:40,120 This warmth significantly speeds up 211 00:35:40,120 --> 00:35:43,280 the development of their eggs. 212 00:35:43,280 --> 00:35:47,400 Even so, they will still take nearly two years to hatch. 213 00:35:49,600 --> 00:35:52,040 Once a female is settled, 214 00:35:52,040 --> 00:35:54,600 she won't move from her spot... 215 00:35:56,080 --> 00:35:58,600 ..not even to feed. 216 00:36:10,120 --> 00:36:14,200 She will constantly tend to her brood – 217 00:36:14,200 --> 00:36:17,120 keeping them clean, 218 00:36:17,120 --> 00:36:19,200 and oxygenating them 219 00:36:19,200 --> 00:36:21,840 with jets of water. 220 00:36:25,480 --> 00:36:30,600 Pearl octopus mothers must surely be amongst the most devoted. 221 00:36:47,880 --> 00:36:53,360 After almost two years, the ordeal take its toll. 222 00:37:00,360 --> 00:37:03,120 But the vigil is almost over. 223 00:38:01,920 --> 00:38:06,280 The last of the brood are gently encouraged to leave. 224 00:38:14,280 --> 00:38:17,240 But this will be a final act. 225 00:38:19,080 --> 00:38:25,360 Like all the mothers here, this octopus is starved and exhausted. 226 00:38:28,520 --> 00:38:31,480 Her life will soon be over. 227 00:38:49,520 --> 00:38:53,160 But this devotion means that her offspring are among 228 00:38:53,160 --> 00:38:58,040 the largest and most developed of any octopus 229 00:38:58,040 --> 00:39:00,720 and have the best chance of survival 230 00:39:00,720 --> 00:39:03,560 in the demanding world of the deep. 231 00:39:19,920 --> 00:39:24,280 We're finding more of these strange hot springs every year. 232 00:39:35,160 --> 00:39:39,120 In some places, they can be astonishingly violent. 233 00:39:40,560 --> 00:39:45,360 Super-heated water – hot enough to melt lead - 234 00:39:45,360 --> 00:39:47,960 spouts from the seafloor. 235 00:39:49,480 --> 00:39:51,960 Dissolved minerals condense around them 236 00:39:51,960 --> 00:39:57,040 to form towering chimneys, known as hydrothermal vents. 237 00:40:01,440 --> 00:40:05,240 They are home to unique communities of animals 238 00:40:05,240 --> 00:40:09,080 that all rely on the nutrients in the scalding water. 239 00:40:19,040 --> 00:40:22,880 Some suggest that vents like these could be the places 240 00:40:22,880 --> 00:40:27,080 where life on Earth first began four billion years ago. 241 00:40:35,120 --> 00:40:38,200 And there is now evidence of hydrothermal vents 242 00:40:38,200 --> 00:40:41,280 on the moons of Jupiter and Saturn. 243 00:40:43,200 --> 00:40:45,960 Could they too be supporting life? 244 00:40:50,600 --> 00:40:54,920 Here on Earth, the influence of these vents 245 00:40:54,920 --> 00:40:57,880 extends far beyond their chimneys. 246 00:40:59,560 --> 00:41:02,880 The essential nutrients carried in these plumes 247 00:41:02,880 --> 00:41:07,800 can rise all the way to the surface two miles above. 248 00:41:13,320 --> 00:41:18,160 Here, they stimulate the rapid growth of tiny marine plants... 249 00:41:18,160 --> 00:41:20,880 ..on an astronomic scale. 250 00:41:27,600 --> 00:41:31,040 This phytoplankton is so abundant 251 00:41:31,040 --> 00:41:35,320 that it produces half of all the oxygen on Earth. 252 00:41:53,400 --> 00:41:58,000 It's also food for a host of minute animals - 253 00:41:59,480 --> 00:42:01,800 zooplankton. 254 00:42:03,560 --> 00:42:07,280 Together, they are the basis of the food chains 255 00:42:07,280 --> 00:42:10,360 that sustain nearly all life in the ocean. 256 00:42:16,040 --> 00:42:19,520 In the Pacific waters off South America, 257 00:42:19,520 --> 00:42:24,480 they feed anchovy that gather here in billions. 258 00:42:37,760 --> 00:42:42,120 This is one of the world's most productive ecosystems. 259 00:42:53,800 --> 00:42:57,440 These South American sea lions are on the hunt. 260 00:43:17,760 --> 00:43:22,680 But the anchovy shoal has already been located... 261 00:43:27,280 --> 00:43:30,680 ..by the planet's most efficient hunters. 262 00:43:34,040 --> 00:43:36,800 A net, over half a mile long, 263 00:43:36,800 --> 00:43:38,760 encircles the shoal. 264 00:43:41,720 --> 00:43:44,800 It can trap over a million fish. 265 00:43:56,760 --> 00:43:59,600 But the sea lions aren't about to go hungry. 266 00:44:01,920 --> 00:44:05,520 They have learnt to look for holes in the net. 267 00:44:16,040 --> 00:44:22,640 Why waste energy when food comes to you as easily as this?! 268 00:44:29,320 --> 00:44:32,600 As more and more sea lions arrive, 269 00:44:32,600 --> 00:44:35,120 some change their tactics. 270 00:44:42,680 --> 00:44:45,720 They line up on both sides of the net... 271 00:44:47,360 --> 00:44:49,200 ..and wait. 272 00:45:03,960 --> 00:45:08,840 As the net tightens, the anchovy panic and rush for the surface. 273 00:45:15,240 --> 00:45:19,360 This is the moment the sea lions have been waiting for. 274 00:45:33,640 --> 00:45:37,400 It's such an effective way of hunting that the sea lions here 275 00:45:37,400 --> 00:45:40,240 are changing their natural behaviour... 276 00:45:43,400 --> 00:45:47,200 ..and are raiding the fishing nets 277 00:45:47,200 --> 00:45:49,640 in their thousands. 278 00:45:57,320 --> 00:45:59,560 With the net almost drawn in, 279 00:45:59,560 --> 00:46:02,800 the fishermen beat out a warning signal. 280 00:46:06,280 --> 00:46:08,280 Time is up. 281 00:46:37,680 --> 00:46:41,800 In the confusion, not everyone manages to escape. 282 00:46:50,400 --> 00:46:54,920 The trapped sea lions are in danger of being drowned. 283 00:47:16,600 --> 00:47:20,360 Pups are separated from their mothers. 284 00:48:24,120 --> 00:48:28,840 Then, at the last minute, the fishermen briefly drop their net... 285 00:48:36,240 --> 00:48:39,360 ..and the trapped sea lions can escape. 286 00:48:47,640 --> 00:48:50,880 But many are not so lucky. 287 00:48:52,760 --> 00:48:57,800 Around the world, millions of animals are accidently caught 288 00:48:57,800 --> 00:49:01,880 and die in fishing nets every day. 289 00:49:04,280 --> 00:49:08,080 And this by-catch, as it's known, 290 00:49:08,080 --> 00:49:11,480 is pushing many species toward extinction. 291 00:49:16,320 --> 00:49:19,720 Animals have evolved in remarkable ways 292 00:49:19,720 --> 00:49:22,360 to the demands of life in the ocean. 293 00:49:27,040 --> 00:49:30,080 But can they now adapt to the new challenge - 294 00:49:31,320 --> 00:49:33,840 living alongside us? 295 00:49:51,040 --> 00:49:54,160 The open ocean is home to some of the largest 296 00:49:54,160 --> 00:49:56,880 and most extraordinary animals on Earth. 297 00:49:59,320 --> 00:50:01,560 But here, off the Canary Islands, 298 00:50:01,560 --> 00:50:05,160 the Planet Earth team are searching for one of its smaller, 299 00:50:05,160 --> 00:50:07,800 and less familiar residents. 300 00:50:07,800 --> 00:50:10,360 We're looking for a tiny creature called a Columbus crab, 301 00:50:10,360 --> 00:50:12,520 which is only about the size of your thumbnail, 302 00:50:12,520 --> 00:50:16,200 which live on floating objects in the open ocean. 303 00:50:16,200 --> 00:50:19,520 Columbus crabs were once only found on natural debris, 304 00:50:19,520 --> 00:50:21,600 like driftwood or seaweed, 305 00:50:21,600 --> 00:50:23,640 but the oceans are changing, 306 00:50:23,640 --> 00:50:25,840 and they've been forced to adapt. 307 00:50:40,240 --> 00:50:44,640 One of the most common items they find is discarded fishing gear. 308 00:50:46,960 --> 00:50:52,240 Over a million tons is left adrift in the ocean each year. 309 00:50:53,800 --> 00:50:56,600 And Columbus crabs are now making their homes 310 00:50:56,600 --> 00:50:59,120 on these unnatural materials. 311 00:51:06,640 --> 00:51:09,920 Surprisingly, Columbus crabs are thriving on this new habitat. 312 00:51:15,200 --> 00:51:20,080 But, for larger ocean creatures, these nets can be lethal. 313 00:51:22,120 --> 00:51:25,760 Loggerhead sea turtles are especially vulnerable. 314 00:51:29,400 --> 00:51:32,800 Many times, they are very injured 315 00:51:32,800 --> 00:51:36,680 and many times they don't even survive. 316 00:51:36,680 --> 00:51:39,200 It's a sad situation. 317 00:51:40,640 --> 00:51:44,640 As a rule, wildlife film-makers observe natural behaviour 318 00:51:44,640 --> 00:51:46,720 and do not interfere. 319 00:51:50,360 --> 00:51:53,680 But this is far from natural. 320 00:51:53,680 --> 00:51:57,120 The team feel they must take action. 321 00:52:06,720 --> 00:52:09,480 Sh... 322 00:52:09,480 --> 00:52:11,840 It seems that the turtle is quite OK. 323 00:52:11,840 --> 00:52:16,480 We'll just finish to cut the plastic and then we release it. 324 00:52:32,920 --> 00:52:35,120 It's a bittersweet moment, 325 00:52:35,120 --> 00:52:40,360 as this is one of eight turtles they rescued whilst filming here. 326 00:52:40,360 --> 00:52:43,680 This situation is not natural, 327 00:52:43,680 --> 00:52:47,440 it's something that is being caused by human beings. 328 00:52:49,040 --> 00:52:52,480 Sadly, the crew now face dilemmas like this 329 00:52:52,480 --> 00:52:55,800 on many of their filming expeditions... 330 00:52:57,840 --> 00:53:01,960 ..including, when they travelled to the Pacific coast of Chile, 331 00:53:01,960 --> 00:53:04,920 to show how sea lions are competing for food 332 00:53:04,920 --> 00:53:07,480 with one of the biggest fisheries on Earth. 333 00:53:12,560 --> 00:53:17,320 Expedition leader Fernando Olivares takes the team to the fleet. 334 00:53:24,520 --> 00:53:28,160 Diving near fishing nets is extremely dangerous, 335 00:53:28,160 --> 00:53:31,720 so the crew must ensure they have the full cooperation 336 00:53:31,720 --> 00:53:33,640 of the fishermen. 337 00:53:58,040 --> 00:54:01,120 Pretty hazardous place to dive. 338 00:54:01,120 --> 00:54:03,440 It's just a case of trying to keep an eye on the divers, 339 00:54:03,440 --> 00:54:06,000 but the sea lions also like to go down and blow bubbles, 340 00:54:06,000 --> 00:54:07,840 so you'll think you're following the divers, 341 00:54:07,840 --> 00:54:10,160 and then a sea lion will pop up. 342 00:54:15,760 --> 00:54:17,880 Taking the utmost care, 343 00:54:17,880 --> 00:54:19,960 the divers get a close-up view 344 00:54:19,960 --> 00:54:22,520 of the sheer scale of the operation. 345 00:54:28,440 --> 00:54:32,000 This one net must have about 15 tons of fish in it 346 00:54:32,000 --> 00:54:35,120 and there's eight or nine boats in this one little bay, 347 00:54:35,120 --> 00:54:36,800 and these are just the small boats. 348 00:54:36,800 --> 00:54:38,880 Out there, there are huge factory ships that are taking 349 00:54:38,880 --> 00:54:41,040 even bigger catches. 350 00:54:42,280 --> 00:54:44,640 How much fish a year from just here? 351 00:54:44,640 --> 00:54:48,480 From a million tons a year more or less. 352 00:54:56,520 --> 00:54:59,160 The catches are so vast, 353 00:54:59,160 --> 00:55:02,280 the sea lions have changed their natural behaviour 354 00:55:02,280 --> 00:55:05,600 to collect anchovies directly from the nets. 355 00:55:09,760 --> 00:55:11,800 But it's a risky strategy. 356 00:55:13,360 --> 00:55:17,320 The crew witnessed sea lions caught in nets multiple times. 357 00:55:18,360 --> 00:55:21,520 Whoa, it's intense mate, there are so many in there. 358 00:55:27,720 --> 00:55:30,320 There's a pup stuck in the net, calling to its mother, 359 00:55:30,320 --> 00:55:33,360 and its mother's just on the outside of the net calling back. 360 00:55:39,640 --> 00:55:42,240 That's really hard to watch. 361 00:55:47,760 --> 00:55:50,040 Oh, the pup's really panicking now. 362 00:55:52,520 --> 00:55:57,040 Sometimes, fishermen are able to release trapped sea lions... 363 00:55:58,360 --> 00:56:00,520 ..but not this time. 364 00:56:02,840 --> 00:56:05,160 The pup is in serious danger. 365 00:56:07,280 --> 00:56:10,960 Once again, the crew decide to step in. 366 00:56:12,840 --> 00:56:16,080 Hey, he's going to go inside of the net to save him. 367 00:56:39,800 --> 00:56:42,040 Wow. 368 00:56:45,880 --> 00:56:49,800 Nice, really nice. 369 00:56:49,800 --> 00:56:51,880 It's a relief this time... 370 00:56:54,400 --> 00:56:59,880 ..but it highlights the new realities of filming wildlife 371 00:56:59,880 --> 00:57:03,520 in today's changing ocean. 372 00:57:12,560 --> 00:57:16,880 Next time, a journey to Earth's greatest wilderness - 373 00:57:20,600 --> 00:57:24,200 deserts and grasslands... 374 00:57:29,720 --> 00:57:33,160 ..where nature puts on its most dramatic show. 375 00:57:36,040 --> 00:57:40,160 Habitat Explorer brings animals and their habitats to life. 376 00:57:40,160 --> 00:57:43,800 Explore this free interactive and make origami animals. 377 00:57:43,800 --> 00:57:47,880 Go to... 378 00:57:47,880 --> 00:57:50,280 And follow the links to the Open University. 379 00:57:50,280 --> 00:57:52,440 Or to order a free printed version, 380 00:57:52,440 --> 00:57:56,200 visit the website or call the numbers on the screen.