Dramatic scenes unfolded at Manly Beach early on Thursday, with swimmers evacuated from the water after a shark sighting.

The shark alarm sounded at the beach early on Thursday as swimmers were embarking on their daily Manly to Shelley Beach swim, news.com.au reported.

Dorsal Watch, a shark reporting and alert solution, reported that a tagged Bull Shark had been detected by the North Steyne receiver just before 8am.

The NSW government’s own Shark Smart also confirmed reports of a bull shark in the Manly area.

One beachgoer told news.com.au that they heard the shark alarm sound this morning and when they looked up, they saw a jetski approaching swimmers.

“It looked like he was driving up to all the swimmers and talking to them, they all started piling onto the jetski,” the witness said.

“There were six or so people that climbed up onto the jetski and he started to drive them back to shore.”

The swimmers were reportedly dropped back to shore, but some defied warnings and kept swimming at the famed beach.

Tweet from @NSWSharkSmart

The shark sighting comes just days after Manly Beach was named the 13th best beach in the world by TripAdvisor.

“A long, wide, sandy beach that sits right on the edge of the Pacific Ocean,” TripAdvisor said.

“There are walking and cycle paths, some green lawn areas, as well as the sandy beach.”

Just last month, several beaches were closed in the area after two bull sharks were spotted at Shelley Beach.

An injured dolphin was seen in the shallows of the beach and eventually died once it beached.