The Deep Ocean Frontier. More people have walked on the moon than have been to the deepest parts of the ocean. Here, film-maker John Ruthven dives to the bottom of the Gulf of Mexico on the mini submersible Johnson Sealink and provides an eyewitness account of the features of the sea floor. He also describes one of the most amazing new habitats recently found on the planet, the "cold vents", where methane gas seeping from the seabed provides energy for a host of newly discovered animals that have never seen the light of day and have developed a new way to live. Producer Julian Hector. Repeated tomorrow 11am