No injuries were reported in the fire, which was reported at 6:01 a.m. at Boat Tree Marina at 4370 Carraway Place near Lake Monroe in Sanford.
Video from Sky 6 showed flames burning the boat and smoke flowing into the air. Firefighters from Seminole County and Sanford battled the blaze from the dock. The marina's manager said no one was inside the boat at the time.
The boat eventually sank as firefighters pumped water onto it because flames kept flaring up.
911 received several calls early in the morning from residents about the fire.
“I was laying here in bed and all of a sudden I heard a great big ‘whoosh’. I looked out the window and the thing was completely engulfed,” one caller said.
In addition to the boat, three pilings, which are support beams for docks, were burned off and a neighboring boat's siding partially melted.
The marina's manager said that usually wind is blowing into the marina, but the morning of the fire, it happened to be blowing away, which kept the fire from blowing into trees and other boats at the dock.
The cause of the fire is not known. Officials said they hope to lift the boat out of the water Thursday night.