RedactedNarrative: On April 26th, 2022 at approximately 2115 hours I received a call from dispatch about a vessel fire at Marathon Yacht Club. When I arrived on-scene the fire had been extinguished by Marathon Fire Department. The vessel had sunk from the stern to midship. TowBoatUS deployed equipment to contain any contaminants that were present in the water and planned to remove the vessel the following day. I spoke with owner after the incident, and he notified me that a fire inspector would be coming to inspect the vessel and locate the origin of where the fire started. Owner made me aware that the fire inspector informed him that the fire originated at the air conditioning unit on the vessel.