The incident occurred at about 4:15 p.m. on Saturday.
The Norwalk Department of Police Service Marine Unit responded as well as Westport and Stamford police and Norwalk fire.
Two men from Long Island, N.Y., were rescued unharmed by the Darien Police Marine Unit, which was the first boat on the scene.
The boat sank in five minutes but remained partially submerged.
Tow Boat US conducted the salvage operation.
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