About 8pm on Monday, the Vic Emergency website said the beach had been closed following a confirmed sighting of a small shark in waters close to the beach.

Life Saving Victoria general manager Paul Shannon said extra lifesaving patrols had been volunteering at the beach due to the warm night.

They had confirmed a sighting of a shark and recommended people didn't swim at the beach for at least two hours, after which time the situation would be reassessed, he said.

Stacey Cohen, of Caulfield, had been at the beach with friends all day before the shark appeared.

"The lifeguards were driving around warning everyone there was a 2.5-metre shark in the area, and all of a sudden it came out of nowhere."

She says it looked "pretty dangerous," but thought it was a little smaller - possibly around the two-metre mark.

The shark drew a huge crowd when it came close to the shore about 7pm, Ms Cohen said.

"Even the lifeguards were in awe," the 28-year-old said.

"I was saying to my friends, I've lived in Melbourne my whole life, but I've never sat on a beach in Melbourne and been warned there's a shark in the area.

"I'm still kind of processing what just happened. It was just the most amazing thing I've ever seen. It was really, really beautiful."

The sighting follows another in early January, when 20-year-old Sophie Hunt, who had been walking along the foreshore, spotted a shark thrashing about in ankle-deep water.

Hunt, who with another passer-by tried to push the blue shark into deeper water, described that experience as surreal.