A 45-year-old man collapsed in the water at Sammy's Beach in East Hampton on Sunday evening and later was pronounced dead at Southampton Hospital, police said.
East Hampton Town Police identified the man as James A. Weber of East Hampton and said they are investigating the case as a possible drowning.
Police said the cause of death will be determined by the Suffolk County medical examiner.
The case occurred near the inlet at Three Mile Harbor at 7:19 p.m., police said.
Police said two men at Maidstone Park Beach saw Weber collapse in the water, swam across the inlet to help him, pulled him unconscious from the water and then performed CPR until emergency personnel arrived.
But, police said, Weber was pronounced dead at Southampton.