Here's what you need to know about shark attacks and how to fight back if you're trapped.
The odds of being attacked by a shark are just one in 11.5 million, but still it's good to know a few tips should the worst happen.
Last year there were 52 shark attacks in the US, while in February this year a surfer died after losing both legs in a shark attack off the northern New South Wales coast.
It was the third fatal attack in New South Wales in the past 12 months and the sixth in Australia.
From 2005 to 2014, an average of six people per year died worldwide after being attacked by a shark.
Tips for surviving
If you find yourself under attack, try and stay as still as possible and make no sudden movements as this could provoke the shark. It's most likely that it will swim away and not bother you. And don't try and out swim the shark.
Take a defensive position by limiting the angles of attack - you can try and find a solid object like a reef to block the shark or another swimmer to swim back to back with.
But, if the shark actually attacks you, fight back. Aim for the eyes and the gills. Use repeated hard jabs with your fist until the shark retreats.
Even if the shark swims away, it could come back, so get to the shore as quickly as possible. Swim with smooth strokes, thrashing around will only attract more attention.