A man was in critical condition after the inflatable vessel he was steering crashed into a docked boat at Sunset Harbor in Huntington Beach, officials said.
The incident was reported around 9:35 p.m. as people in the water screaming for help, according to Carrie Braun, a public information officer with the Orange County Sheriff's Department.
Responding deputies found a man and a woman who had fallen from the 13-foot inflatable craft, though it was unclear if it was the force of the collision that knocked them in, Braun said.
The man driving the vessel was underwater for at least 10 minutes. He was rescued and taken to the hospital in critical condition, authorities said.
The woman was not injured and speaking with investigators. Deputies did not believe anyone was aboard the docked boat involved.
It was unknown whether drugs or alcohol played a role in the incident, officials said.
Detectives were responding to the scene to investigate, and no further details were available.
KTLA's Matt Phillips and Anna Albaryan contributed to this report.