A fisherman was plucked from the chilly waters off Montauk Point Saturday afternoon by a Coast Guard crew after an alert bird-watcher reported seeing someone clinging to a life raft, authorities said.

The identity of the fisherman, 52, was not made public. He told the rescuers that his 38-foot vessel had capsized and sunk about six miles from Montauk Point, Coast Guard officials said. The man was treated for hypothermia and hospitalized.

He was taken to Southampton Hospital, then airlifted to Stony Brook University Hospital, where his condition was not known, officials said.

The bird-watcher was in the vicinity of Montauk Harbor when she noticed "a person in the water" and relayed a message to a local restaurant, officials said. A 47-foot Coast Guard rescue boat from Station Montauk, which was in the midst of training, headed to the location, officials said.

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"Fortunately we were in the area conducting training at the time of the report and were able to quickly respond to the location of the person in the water, especially since we were quickly losing valuable daylight to search for the fisherman," said Coast Guard Petty Officer 2nd Class Brent Walsh in a statement.

The Coast Guard said an investigation was underway.