(ABC News) -- The Coast Guard was searching today for a man who went overboard from a Royal Caribbean cruise ship as it headed towards Puerto Rico.
The Adventures of the Seas cruise ship was in Mona Passage headed toward San Juan, Puerto Rico, Saturday night when a passenger alerted the captain that they had seen another passenger go overboard, according to an email from Royal Caribbean spokeswoman Cynthia Martinez.
The captain immediately turned the ship around and alerted authorities.
The Coast Guard identified the passenger as 26-year-old Tien Phuoc Nguyen, who was on the cruise with his family.
Nguyen, a Canadian citizen, was seen by other passengers jumping overboard at approximately 8:46 p.m. Saturday. According to Martinez, closed-circuit cameras aboard the ship also caught Nguyen going overboard.
As soon as the Coast Guard was notified, an Air Station Borinquen MH-65 Dolphin helicopter was launched and the USCG Cutter Cushing was diverted to search for him.
"We will continue to search until we determine that all probability of survival has been extended," Coast Guard spokesman Ricardo Castrodad said.
Searchers are still hopeful about Nguyen's chances of survival, but the weather in the into Mona Passage area is unpredictable and the seas are often dangerous, he said.
"Weather conditions there typically change rapidly. It could be a good weather day and a weather system comes in and everything turns and becomes pretty nasty," Castrodad said.
"You can have easily from two to four feet seas and then be facing 10-foot seas from one moment to another, so it is known as a pretty dangerous body of water," he said.
While the Coast Guard searches for Nguyen in the water, the FBI is investigating what might have led him to jump overboard.
After the Coast Guard took over the search for Nguyen, the Adventure of the Seas cruise ship was allowed to continue to port. On Saturday the ship was returning from a week-long cruise with several scheduled stops in the Caribbean.