January Jones isn't a ''daredevil.''

The 'Last Man on Earth' actress is a vocal supporter of the largest international ocean conservation and advocacy organisation, Oceana, but admits she can get ''a little claustrophobic'' in the water.

Speaking at a charity event in Beverly Hills to help raise funds and awareness for conserving the open waters, she said: ''I'm not a daredevil. I like jet skiing. I don't love to scuba dive. I just get a little claustrophobic. When I do trips with Oceana, I usually free dive and hold my breath. [I can't hold my breath] for too long. It would be like a minute, tops.''

But the 37-year-old star admits her four-year-old son, Xander, is a lot more courageous and is desperate to go swimming with sharks.

She said: ''We read a lot of books about sharks and dinosaurs. He wants to go swimming with sharks with me, but I've told him he has to wait until he's 10. It's a fair age, I think. But he can go on tagging trips on the boat maybe.''

The former 'Mad Men' actress doesn't expect Xander to follow in her footsteps by becoming an actor.

She told PEOPLE.com: ''He knows all the names of every dinosaur, and he wants to be a real dinosaur scientist when he grows up. Not a paleontologist, but a scientist for real dinosaurs. So, he's dreaming big.''