A West Islip man whose boat capsized in the Great South Bay was rescued by a towboat captain Saturday evening, Suffolk County police said.

Douglas Hassell, 51, was west of the Robert Moses Causeway, off Babylon, when he noticed his 20-foot Sportcraft boat quickly taking on water, police said.

He dialed a number for TowBoatU.S., a marine towing service, which dispatched a boat and notified the U.S. Coast Guard.

Suffolk County police Marine Bureau officers heard the Coast Guard's radio request for help, and began boating to the location. Suffolk also dispatched another rescue boat and a helicopter, police said.

Hassell put on a personal flotation device and climbed onto the overturned hull of his boat after it capsized, police said.

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Suffolk police said a captain with Bay Shore-based Reynolds TowBoatU.S. arrived shortly before a police boat and the U.S. Coast Guard, and took Hassell aboard.

Hassell was not injured, police said. His 1987 boat was towed by Reynolds.

Suffolk police said the best way to call for help on the water is to dial 911 or call the U.S. Coast Guard on radio channel 16. New York State law mandates that anyone in a boat less than 21 feet -- including canoes, kayaks, rowboats and motorboats -- that is underway must wear a life jacket between Nov. 1 and May 1.

The Great South Bay is currently about 50 degrees and the Long Island Sound and Atlantic Ocean are about 43 degrees, police said, warning of the cold water temperatures.