The Long Beach Fire Department responded to reports around 9:20 p.m. on Wednesday that a 48-foot boat had crashed into the Alamitos Bay jetty, officials said Thursday.
The Fire Department said speed was likely a factor.
All 10 people who were injured were taken to hospitals. Three remained in critical condition on Thursday afternoon.
The deceased man was identified only as a local real estate agent.
"So far what we know is that the vessel, or in this case the yacht, was traveling at a high rate of speed," said Petty Officer 3rd Class Richard Uranga, a spokesman for the U.S. Coast Guard. "We don't know what speed that was but unfortunately it hit the jetty."
A jetty is a long, narrow structure that extends from shore into water.
The cause of the crash remains under investigation.