A 28-year-old man who fell off a cruise ship has been rescued after 15 hours at sea.

After cruising on Carnival Valor in the Gulf of Mexico the man went missing after going to use the toilet at a bar. Around 15 hours later he was spotted and rescued about 30 kilometres off the coast of Louisiana.

Lieutenant Seth Gross from the US Coast Guard described being in the sea that long and surviving as the “absolute longest that I’ve heard about – and just one of those Thanksgiving miracles”

Mr Gross said he’s never seen something like this in his career before and that the rescue “shows the will to live is something that you need to account for in every search-and-rescue case”.

The passenger, according to the Coast Guard turned out to be James Grimes, 28 who had been travelling with his parents and siblings on a five-day cruise.

His family had seen him the night before around 11pm. But by 10:45am on Thanksgiving morning when his family found no traces of him, they alerted the crew of the Carnival Valor.

Later that evening, at around 8:10pm more than nine hours after his family reported him missing, a tanker spotted Mr Grimes near the mouth of the Mississippi River and alerted the Coast Guard.

Mr Gross also said the exact timeline and nature of the incident are still unknown.

“We have not been able to confirm when he entered the water, so we’re under the assumption [that] at any point from Wednesday on, he could have entered the waterway.

“He realistically could have been in the water for 15+ hours before we were able to successfully rescue him.”

It isn’t yet known how the man fell off the ship but he is currently in stable condition. However, he was suffering from hypothermia and dehydration when rescued and is currently receiving treatment at a hospital in New Orleans.

His family described Mr Grimes as an exceptional swimmer and had treaded in 65- to 70-degree water for hours, withstanding rain, wind and three to five foot waves where bull sharks and black tip sharks are commonly found.

The cruise ship initially turned around to search for him, but later turned back as the Coast Guards released them from searching.

The dramatic footage shows the man being remarkably hoisted out of the dark ocean, being eventually bundled into the rescue helicopter.

You can watch the incredible footage below.