Fire crews responded to reports an 11 metre cabin cruiser was up in flames about 70 metres off the shore from Wangi Workers Club just after 2am.
However crews couldn't reach the vessel and an RFS boat from Wyee had to be brought in to fight the blaze which had been burning fiercely for up to 45 minutes by the time they arrived.
They managed to extinguish the fire but the cruiser was burnt to the waterline and sank in 5 metres of water as it was being towed to a nearby jetty.
It's not clear at this stage if anyone was on board the boat when the fire broke out.
The RFS says 2 or 3 other boats including a 30 foot cruiser were scorched by the intense blaze.
There is a large amount of fuel debris in the water.
Hazmat crews have recovered 2 gas cylinders - they say fuel is being dispersed by the wind and tide.
An RFS Boat Was Called In To Tackle The Blaze |