A Santa Rosa man who jumped off a boat on Lake Sonoma Sunday afternoon to retrieve an inner tube foundered in the water, sank and died, according to the Sonoma County Sheriff’s Office.

David Hartsough, 50, was one of four people on a jet boat on the Warm Springs arm of the lake when the engine died and the boat went adrift, said Sheriff’s spokesman Sgt. Spencer Crum. An inner tube was knocked into the water by either the wind or a wave, Crum said, and as soon as Hartsough dove into the water to retrieve it he began yelling for help.

A woman jumped off the boat and was able to reach Hartsough just as he went under water and she saw he wasn’t breathing, Crum said.

A nearby boat was flagged down and Hartsough was brought to a private marina where CPR was conducted until paramedics arrived. He was pronounced dead at the scene.

The cause of death is under investigation by the Sonoma County Coroner.

You can reach Staff Writer Nick Rahaim at 707-521-5203 or nick.rahaim@pressdemocrat.com. On Twitter @nrahaim.