Police are trying to determine whether a body found floating in the ocean off southern Sydney is that of missing university student Jamie Gao.

A body wrapped in a blue tarpaulin, spotted off a Sydney beach, could be that of missing man Jamie Gao.

The body was spotted in the ocean off Shelly Beach at Cronulla about 7.30am on Monday.

The discovery came after former NSW detective Glen McNamara was charged over the alleged murder of Mr Gao, a 20-year-old Sydney university student, who was went missing last Tuesday.

Detective Superintendent Luke Moore confirmed investigators were trying to determine the identity of the body, which was pulled out of the ocean after 9am.

Lachlan Steven told Fairfax Media he spotted a body wrapped in a blue tarpaulin while on a boat heading to Sydney Harbour.

Mr Steven saw two feet with white runners on and described the body was small.

“The (body) was pretty short … a very small body,” he said.