A cruise ship pianist has been rescued after spending approximately nine hours in the Pacific Ocean after falling overboard while working aboard a Royal Caribbean vessel off the coast of California.

The unidentified man was discovered by two fishermen around 20 miles (32 kilometres) from the Californian coastline near Catalina Island on Friday.

According to US media reports, the crew member had been in the water for several hours before fishermen Grant Garrett and Sean Norton spotted him while out at sea.

The two fishermen said they immediately stopped their boat and moved to rescue the struggling man after realising that what they had spotted in the water was a person.

The man, who later identified himself as a pianist aboard Royal Caribbean's Ovation of the Seas cruise ship, was reportedly conscious when the fishermen pulled him out of the water.

Norton said the rescued crew member appeared relieved after being brought aboard their boat, with his first words expressing gratitude for the rescue.

The United States Coast Guard confirmed that it had received a report from a member of the public who had recovered a conscious individual from the ocean.

The man was subsequently handed over to Newport Beach Lifeguards before being taken to hospital, where he was reported to be in stable condition.

Newport Beach Lifeguard Battalion Chief Adam Yacenda said preliminary information suggested that the pianist may have fallen overboard at approximately 2:30am, about nine hours before he was discovered.

Yacenda estimated that the rescue took place between 15 and 20 miles offshore, describing the location as being almost in the middle of the ocean.

The circumstances surrounding how the crew member ended up in the water remain unclear, with the US Coast Guard confirming that investigations into the incident were ongoing.

The fishermen also credited the unusually warm ocean temperatures for helping the man survive the lengthy period in the water.

Norton noted that the Pacific waters were significantly warmer than usual, which may have increased the crew member's chances of survival.

He added that the man might not have survived such a long period in the ocean under different weather conditions.

Royal Caribbean Group confirmed that the rescued man was one of its employees and said the company was providing the necessary support during his recovery.

The company, however, declined to provide further details about the incident, citing the employee's privacy.

The rescue comes amid growing attention to the developing El Niño climate phenomenon, which scientists monitoring the Pacific say has been associated with exceptionally high ocean temperatures.

The warm waters, which reportedly reached approximately 24 degrees Celsius in the area where the pianist was found, are believed to have played a role in his survival.

The incident has drawn attention to the dangers faced by people who fall overboard from cruise ships, particularly when they are far from shore and remain undetected for several hours.