A sailor who was woken by snoring found a baby sea lion asleep on a bunk in his boat.

Michael Duffy, 48, was on his 41ft Kettenburg boat Elixir at the San Diego Yacht Club when he awoke at 2.30am local time on Sunday.

Hearing snoring and sneezing, he thought it might be friend crashing from a night out, but could not find anyone.

Once it got light a few hours later, however, he heard it again, and that is when he found a 35lb sea lion pup on another bunk, curled up like a dog on top of his board shorts.

"It was a tiny little guy, and I was kind of shocked, but he was basically asleep," Mr Duffy said, guessing it was a male.

"Then he heard me coming, so he kind of looked up a little bit like when a dog is sleeping and you want to wake it up and it doesn't want to wake up."

He said the pup was probably looking for his mother but found him instead.

The incident happened on Mother's Day in the US, and Mr Duffy grabbed his mobile phone and took a photo of the pup, who had already jumped down onto the cabin floor.

The advertising copywriter, has been sailing since he was aged six, and has grown up around the marine environment, said he had heard of sea lions getting onto boats, but never going down below.

"Totally bizarre," he said, adding: "Sea lions they can be cute, but they can be dangerous. You've got to be careful it's a wild animal."

If the sea lion had been an adult, he would have stayed away. But, he said this pup was very well behaved and left no mess, not even seawater on his shorts.

He said the pup had an orange tag on its flipper and he believed it may have been once rescued after washing onto the shore, before being set free again.

The baby sea lion appeared to be healthy and swam fine, and it was seemingly no stranger to humans.