Autistic man missing after jumping overboard on cruise ship

The man went overboard after climbing over a deck rail of the Carnival Fantasy cruise ship. Photo / Supplied

An autistic man missing at sea since Sunday, when he disappeared from a Carnival Cruise Line ship traveling from Alabama to the western Caribbean, went overboard after climbing over a deck rail, the company said Wednesday.

The family says he is presumed dead.

Relatives of the 22-year-old Johns Creek, Georgia, man believed "he may have been under the mistaken assumption that he was going swimming," the Miami-based company said in a release.

The cruise line also provided a statement from the family of Luke Renner that said relatives were devastated by his death but do not blame a group that organised the trip for people with special needs, Wishes4Me.

"He loved the Wishes4Me special needs community where he lived, and we were delighted when they planned this special event. He loved cruises," said the statement, sent by a public relations firm.

An earlier statement from the cruise company said crew members aboard the Mobile, Alabama-based Carnival Fantasy conducted shipwide searches and made onboard announcements after a passenger disappeared Sunday while the ship was headed to Progreso, Mexico.

The man was travelling with an organised group of nine people with three chaperones, the company said, and he was last seen when he ran out of his cabin.

A chaperone could not locate him and contacted the crew.

While the ship was docked at Progreso, the Mexican Navy helped with a canine search that didn't turn up signs of the man.

The Fantasy left Mobile on Saturday on a cruise across the Gulf of Mexico. It has a passenger capacity of 2675 people.

- AP