Seven people have been taken to hospital, including one with smoke inhalation and superficial burns, after the boat they were in burst into flames off The Bluff on Tuesday, March 31.
Two Metropolitan Fire Service (MFS) crews, paramedics and police were called to the scene at Encounter Bay about 9am after the 6.5m boat's engine caught alight.
Witness Richard Hagan said he saw the boat coming in from behind The Bluff and went to take a photo because it looked picturesque, but as it motored past Wright Island a plume of white smoke came from the engine.
"I'd seen the smoke, then there were foot-long flames coming from the engine," he said.
"Everyone was squealing and then I saw four people jump off. When they jumped off, some other boats were there within two minutes."
He said one boat came out to help from the boat ramp, while another already in the water nearby also assisted.
An SA Police spokeswoman said seven people - a combination of adults and children - were on board at the time.
An SA Ambulance spokeswoman confirmed one person had sustained superficial burns and smoke inhalation, but all seven people had been taken to South Coast District Hospital for assessment.
The boat drifted into shore off The Bluff, where MFS crews secured it and let a large amount of fuel burn before extinguishing it.
Police say the cause had not been determined, but believed it was not suspicious.
The damage bill is estimated to be $70,000.