Lake Macquarie Fire Boat and multiple firefighting crews were called out late on Thursday night to a boat on fire off Summerland Point.
The alarm was raised at about 11pm on September 5 when the vessel was seen well alight on a mooring off Kullaroo Rd.
A crew of five on Fire Boat Alpha responded along with Rural Fire Service crews from Wallarah, Gwandalan Summerland Point, Lake Munmorah, and the Fire and Rescue team from Doyalson.
On arrival Wallarah crews quickly got to work utilising the monitor to combat the fire initially before transitioning to a hose line once safe to come alongside.
Unfortunately, given the extent of the damage to the vessel and a small section burning to the waterline, the yacht was taking on water.
A short time later the vessel sank.
Crews used an anchor and fender to give a visual location of the sunken vessel along with GPS co-ordinates in order to facilitate a later salvage operation to remove the vessel.