In a Facebook post, Branford Fire Department said they were dispatched at 1:19 p.m., with the U.S. Coast Guard responding along with mutual aid from Guilford Fire Department.
In photos sent to News 8, marine units could be seen working to put out the blaze with a large black cloud of smoke coming from the boat.
Branford Fire Department said eight people were rescued by civilian boats and transported to shore by the Coast Guard; they were all taken in safely. No injuries were reported.
Despite efforts from Branford Fire Department, the fire was too unsafe for boarding to reach the seat of the fire. Branford Fire Department said the boat eventually sunk.
The Department of Energy and Environmental Protection responded to the scene to address environmental issues.
The cause of the fire is unknown at this time.