Diving in the Indian Ocean, Hans and Lotte Hass and their party bring up various animals to study on board the Xarifa. There are living corals-what limits the depth at which they can build reefs? There is a spider crab which fixes on its own camouflage; and there are families of clown fish living in sea anemones and illustrating nature's ruthless system of survival by competition.
Directed and produced by Hans Hass in association with the BBC Natural History Unit