Firefighters with the Orange County Fire Authority responded just after 10 a.m. with a helicopter and swift water rescue team but realized the man was dead when they reached him near Cerritos Avenue, said Capt. Thanh Nguyen.
The discovery was made as a storm system moved through Southern California, increasing water levels in local creeks and channels.
Los Alamitos Police Department officials said the man’s death appears to be accidental but an investigation has been launched.
“We don’t suspect any foul play,” said Robert Acosta, a spokesperson with the Police Department.
Investigators are canvassing the area and looking for cameras to determine how the man ended up in the water, he said.
The man was identified only as a 63-year-old from Buena Park. Acosta said police were withholding his name until next of kin could be notified.
Officials spotted the man drifting down the creek Thursday morning, and there was no indication he was conscious when he was found in the water, Acosta said.
“All indications are that it was an accident, but we have to make sure,” he said.