Sylvia Earle - Oceanographer
Sylvia Earle is one of the world's most remarkable marine scientists and explorers.
In her five decades of diving she has done some of the deepest and most-challenging dives in history.
Her work has led her to catalogue increasing declines in the world's stocks of fish and coral.
Now aged 77, she talks to Stephen Sackur about her life and work as an oceanographer and explains why she thinks our planet is in grave peril.