Dirk Denny, 49, was found face down in the ocean Saturday afternoon, Marin County Fire Department spokesman Mike Giannini said.
Denny was wearing a wetsuit and had been surfing, Giannini said.
After efforts to resuscitate him failed, Denny was taken by medical helicopter to Petaluma Valley Hospital, where he died at 5:30 p.m.
An autopsy was performed Monday and the Sonoma County coroner's office is awaiting toxicology test results to determine his cause of death.
Denny owned Denny Painting and had painted homes in Marin County and San Francisco for the past 30 years, according to the company's Web site.