A large shark has startled swimmers who found the predator inside a swimming enclosure off South Stradbroke Island.

The bull shark, which was about 1.5 metres in length, is believed to have jumped over the swimming enclosure’s inflatable perimeter, Gold Coast City Council told nine.com.au.

“With the increased activity of bait fish in the water at this time of year, it’s not unusual for bull sharks to breach out of the water,” a council spokesperson said.

Dozens of sharks were spotted circling and feeding off the coast of North Stradbroke Island last week.

The council deflated the perimeter floats, allowing the enclosure nets to fall to the bottom and the shark to return to the open ocean.

“Officers inspected the nets and found no damage or holes. Officers also snorkelled the entire enclosure and confirmed the shark was no longer within the enclosure,” the spokesperson said.

Footage of the shark enjoying its swim around the Tipplers swimming enclosure went viral.

Jeanette Haskew, who filmed the video, told 9NEWS her daughter normally jumps straight in.

"It's a bit of a scary thought," Ms Haskew said.

"It was circling the net trying to get out, it was coming right up to the shoreline and turning around, yeah it was quite a surprise".

Young Gracie knew swimming with a shark was a risky move, telling her mother, “I can’t swim in there”.