A man who fell overboard during a vacation cruise in the Gulf of Mexico has been rescued after several hours in the water off New Orleans, authorities said Friday.

The 28-year-old, who was not publicly identified, may have been in the water for at least six hours when he was pulled from the sea on Thursday. He was rescued about 20 miles south of the Louisiana Southwest Passage, where the Mississippi River meets the coast, US Coast Guard officials said.

The man’s survival was hailed as unlikely and possibly miraculous given how long he may have been in the water. Coast Guard Petty Officer Ryan Graves said the man did not have a flotation device and it is unlikely he would survive at sea without one.

«It makes it all the more miraculous that we were able to find him conscious and floating in the water,» Graves said.

The cruise passenger was last seen aboard the Mexico-bound Carnival Valor around 11 p.m. Wednesday, Graves said.

Coast Guard rescue teams pulled the man to safety six hours after receiving a report at 2:30 p.m. Thursday that a passenger had gone overboard, Graves said.

It is not clear how or when the man fell overboard. Carnival Cruise Lines said in a statement that an accidental fall overboard would be rare and physically challenging.

«Cruise ships have safety barriers in all public areas that are regulated to US Coast Guard standards that prevent a guest from falling,» it said Friday. «Guests should never get on the rails. The only way to fall overboard is to climb on purpose and over the safety barriers.»

Nighttime video from a Coast Guard plane appears to show the man struggling in relatively calm but active seas, where his head plunged below the surface with each wave. The agency said in a statement that the passenger was «receptive» when crew aboard an MH-60 Jayhawk helicopter caught up with him.

Surface temperatures in the gulf are about 70 degrees, Gross said. Data from coastal monitors, buoys and oil rigs collected by federal meteorologists and the Scripps Institution of Oceanography measured water temperatures Friday from 63 degrees near shore at Southwest Pass to 70 and higher at sea.

Graves noted that in early October, even some of the warmer seasonal waters challenged three men who spent 28 hours at sea, 25 miles off the Louisiana coast, after the boat they were using capsized in rough seas.

The water was warm, he said, but the trio were beset by signs of hypothermia when they were rescued by Coast Guard crews on October 9.

The average October sea temperature near the coast at Mobile State Docks, Alabama, is almost 77; it was slightly above 62 there on Friday, according to the National Centers for Environmental Information.

Experts have suggested that it is not likely to survive in water that is 60 degrees or below after six hours, but warmer water may increase its chances of doing so. Cold shock, failure to swim, and hypothermia it can open the pathways to death, including drowning and cardiac arrest.

T.J. Swigart contributed.