For 40 years oceanographers in the United States have been exploring the deep oceans in Alvin -the first manned deep-sea submersible vehicle. After a long career Alvin is to retire and be replaced. Quentin Cooper is joined by Dr Bob Detrick and by Dr Bramley Murton to talk about the discoveries made in Alvin and to look to the future of Deep Submergence Vehicles. producer Pamela Rutherford