Lewis Pugh has followed an unspoken rule during his career as one of the world’s most daring endurance swimmers: Don’t talk about sharks. But he plans to break that this week on a swim around Martha’s Vineyard, where “Jaws” was filmed 50 years ago.

The British-South African was the first person to complete a long-distance swim in every ocean of the world — and has taken on extreme conditions everywhere from Mount Everest to the Arctic.