Unique fish tornado captured by free-diver

He's one of the world's leading marine photographers, a champion free-diver and an active campaigner against the cull of sharks.

But recently, on a trip tracking sharks off Baja California, Canadian-born William Winram became a mere spectator to a unique phenomenon called a fish tornado.

While it may look like a defence mechanism, the reality couldn't be further from this. The movement is an act of courtship, which doesn't usually happen in such a large scale.

The name "fish tornado" was coined by marine scientists due to the swirl which surrounds the fish, usually bigeye trevally, when they start their amorous movements.

William, 50, captured the images as he held his breath under the water for minutes at a time.

He said: "All in all, it was impressive to see the changes in the area for the better and to also see that it is the local population that is managing, protecting and enforcing within the marine protected area."