A pianist for a Royal Caribbean cruise ship is expected to survive after two Newport Beach, California, fishermen discovered him treading water in the Pacific Ocean nearly 20 miles (32km) offshore on Friday.

The unidentified man was taken to the hospital after the rescue, according to the US Coast Guard, which is now investigating how he went overboard from the cruise ship.

Authorities believe the man may have been in the ocean for approximately nine hours before he was spotted by Sean Norton and Grant Garrett, who were returning from a fishing trip near Catalina Island.

The two fishermen had spent the morning fishing for marlin when their trip took an unexpected turn. By noon, they had pulled the stranded man from the water.

“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 the boat’s captain first saw the man in the water.

The fishermen quickly worked together to bring the man onboard. Once the man regained his composure, Garrett said he identified himself as a pianist onboard Royal Caribbean’s 14-deck cruise ship, the “Ovation of the Seas.”

According to Norton, the rescued crew member had few words to describe what he had just experienced. “The only thing he said to me was, ‘Thank you. I thought I was gonna die,’” Norton said.

After the rescue, the fishing crew issued an emergency maritime call, prompting Newport Beach lifeguards to respond and provide assistance. Battalion chief Adam Yacenda said the man was found approximately 15 to 20 miles offshore, according to CBS, or “pretty much in the middle of the ocean”.

Despite the extended time spent in the water, Norton believes unusually warm ocean temperatures may have played a significant role in the man’s survival.

“You have this crazy super El Niño year. This guy was in the water for probably 10 hours, but the water’s 76 degrees,” Norton said. “A different year, no way he makes it.”

The circumstances surrounding the crew member’s fall from the cruise ship remain under investigation by the Coast Guard. Royal Caribbean Group acknowledged the incident and said it is assisting the employee following the ordeal.

In a statement to CBS, a company spokesperson said: “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.”