Ocean Deep | Planet Earth Ep. 11

The final instalment concentrates on the least explored area of the planet—the deep ocean. It begins with a whale shark used as a shield by a shoal of bait fish to protect themselves from yellowfin tuna. Also shown is an oceanic whitetip shark trailing rainbow runners. Meanwhile, a 500-strong school of dolphins head for the Azores, where they work together to feast on scad mackerel along with a flock of shearwaters. Down in the ocean's furthest reaches, some creatures defy classification. On the sea floor, scavengers such as the spider crab bide their time, awaiting carrion from above. The volcanic mountain chain at the bottom of the Atlantic Ocean also sustains life through the bacteria that surround its sulphide vents. There are thought to be around 30,000 undersea volcanoes, some of them taller than Mount Everest. Their sheer cliffs provide anchorage for several corals and sponges...