In similar but separate incidents on New Year's Day, authorities say a California man and UK man were both swept out to sea by what were described as rogue waves.
Both men were reportedly walking their dogs when the incidents occurred.
The Coast Guard says a unidentified California man and his wife were walking on the beach near Point Reyes, a popular tourist destination about 30 miles northwest of San Francisco, around 12:30 p.m. PST on New Year's Day, when a wave overtook their dog.
The San Francisco Chronicle reports the couple went into the water to rescue the dog but the man was swept away.
His body was found about three hours later. The wife and dog made it safely to shore.
The National Weather Service in nearby San Francisco had issued a small craft advisory including the Point Reyes area for hazardous seas of eight to 13 feet from 8:38 a.m. to 3 p.m. PST Tuesday. These conditions likely led to the deadly wave.
In the second incident, the BBC News reports Paul Morris, 41, was washed into the sea by a rogue wave while walking a dog with a friend in the early hours of New Year's Day in Blackpool, a borough seaside town, and unitary authority area of Lancashire, in North West England.
A Lancashire Police spokeswoman said: "The man and a friend were walking a dog along steps leading from the Promenade to the sea, close to the Central Pier on South Shore, when a wave washed them into the sea."
"His friend has managed to climb out of the water but sadly Paul did not emerge."
The man remains missing and coast guard officials say it is highly unlikely that the man will be found alive.
Gale force conditions were described to be hitting the area at the time, which more than likely churned up the deadly wave.