Boy still serious after Straddie boat fire

A five-year-old boy remains in hospital with serious burns to his face and body after a speed boat exploded off Queensland's South Stradbroke Island.

The boy was one of five people treated in for serious burns following the explosion near Tipplers Beach on Sunday at around 10am.

An off-duty Gold Coast police officer was among the injured.

Jet skiers created waves to try to extinguish the blaze before firefighters could get to the scene.

A witness said they heard a loud boom.

"They were just diving out the side of the boat, trying to get away from the flames."