A cruise ship pianist reportedly treated water for nine hours before he was rescued by passing fishermen in the middle of the Pacific Ocean off California.

The 37-year-old man was miraculously discovered when Sean Norton and Grant Garrett were fishing for marlin some 32 kilometres off Southern California, near Catalina Island.

“I’m like, ‘Yeah, it’s a human being. Stop the boat; let’s get all of our lines in’,” Garrett told CBS News, recalling the moment they spotted the drifter on Friday (local time).

Added Norton: “Grant and I each got an arm and lifted him up. He was in total shock.”

When the man regained consciousness, he told them he was a pianist on the 14-deck Royal Caribbean cruise ship Ovation of the Seas.

“The only thing he said to me was, ‘Thank you. I thought I was gonna die,'” Norton said.

CBS News reports that after pulling him from the water, the fishermen put out an emergency maritime call, and a group of Newport Beach lifeguards responded.

“It was approximately 15 to 20 miles offshore, pretty much in the middle of the ocean,” Battalion Chief Adam Yacenda said.

The man said he worked on the Ovation of the Seas, which has 14 decks. Photo: Royal Caribbean website

It was believed the pianist may have gone overboard from the ship about nine hours before he was found, at around 2:30 am.

The man was hospitalised and expected to survive. The US Coast Guard is investigating the incident.

The Royal Caribbean Group told CBS LA: “We are providing support and assistance to our crew member during this difficult time.

“To respect the privacy of our employee, we have no additional details to share.”