Young boy among five burned in Queensland boat fire

A five-year-old boy and four adults have suffered significant burns after a boat fire off Queensland's Stradbroke Island.

Authorities believe the boat went up in flames near Tipplers Beach around 10am.

The engine is thought to have exploded when the family on board tried to restart it.

They swam to safety and were hauled by bystanders onto a large cruiser, who helped them until emergency responders arrived on the scene.

Paramedics treated the boy, a man, and three women for serious burns sustained on the vessel. 

The child was airlifted by helicopter to Lady Cilento Children's Hospital. 

A 20-year-old woman and a 50-year-old man were also airlifted to Royal Brisbane and Women's Hospital. 

The remaining 19-year-old woman and 26-year-old woman were taken to Gold Coast University Hospital and Royal Brisbane and Women's Hospital respectively. 

The boat is now beached as police investigate.