In the video, the man swims in medium-deep water as a nurse shark gets closer and closer.
If the pair pass within a few feet of each other, the shark loses interest and turns away.
Loughlin estimated the shark at “about two meters”.
“The shark just emerged from the whitewash in the water up to the waist,” he told 9news.com.au.
“It was exciting to watch from above.
Mr Loughlin said it is unusual to see the species so close to shore.
“These are nurse gray sharks. Usually they are very chilled (but) they are not often seen on Maroubra beach cruising in the shallows,” he said.
“Apparently the shark has no interest in the swimmer.
“I’ve seen a lot of shark behavior from above and in most cases they just mind their own business and happily share their waters with visitors like humans.”
The Department of Primary Industries (DPI) says nurse sharks have an unfortunate history in NSW.
After being falsely accused of a series of attacks on Sydney’s beaches in the 1950s and 1960s, the sharks were “executed at every possible opportunity”.
In the late 1970s, it was discovered that the species was not a “man-eater”.
After much lobbying, nurse sharks become the world’s first protected shark species.
However, recent surveys show that NSW’s populations have not recovered and the species is considered “endangered,” the DPI said.