The Coast Guard rescued a 36-year-old man at around 4 a.m. Tuesday after they found him clinging to the hull of his capsized 10-foot aluminum boat on the Bass River near South Yarmouth.

The man’s girlfriend had alerted authorities at 1:20 a.m. that he had not come home, the Coast Guard said in a statement.

The Coast Guard launched a 42-foot rescue boat around 2 a.m., and a Coast Guard helicopter joined the search an hour later.

At about 4 a.m., the man was located and pulled from the 37-degree water, the Coast Guard said.

Helicopter video provided by the Coast Guard showed the man on top of his boat in a vast expanse of water as the rescue boat approached. The crew could be seen dragging him aboard and trying to warm him up.

The man’s condition was not immediately available.

Maddie Kilgannon can be reached at maddie.kilgannon @globe.com. Follow her on Twitter @MaddieKilgannon.