A Connecticut man died after he was unable to swim back to his boat that was anchored in the Long Island Sound off Plum Island, Southold police said Wednesday.

Police identified the man as Harold Calkins, 63, of Stonington.

The incident happened about 12:45 p.m. Tuesday when Calkins got caught in a current after diving off his boat, a police spokesman said.

The U.S. Coast Guard found Calkins and transported him to Eastern Long Island Hospital in Greenport, where he was pronounced dead, the spokesman said.

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The cause of death was being investigated by Suffolk County Medical Examiner’s Office, but no other details of the incident were available, the police spokesman said.

A Coast Guard spokesman said they “assisted” in the incident, but also had no further details.