James Michael Grimes went overboard a cruise ship and treaded water for 20 hours.
A US Coast Guard rescue coordinator told Insider every factor went right for him to survive.
"This is definitely the top end of the survival limit," Lt. Seth Gross said of Grimes.
A 28-year-old man who fell off a cruise ship the night before Thanksgiving miraculously survived because a "whole bunch of factors" worked out "perfectly," according to a US Coast Guard search and rescue mission coordinator.
James Michael Grimes was found by a bulk carrier vessel, a harrowing 20 hours after he fell off the Carnival Valor on the night of November 23. Lt. Seth Gross oversees search and rescue missions in the greater Louisiana Gulf Coast area, and said his rescue crew arrived just in time to save Grimes' life.
But "to survive the fall, to be able to keep himself afloat, that no sharks ended up locating him, and then this motor vessel just happened to be in the right position" all worked to keep him alive until the team rescued him, Gross told Insider.
Grimes was last seen around 11 p.m. and was reported missing the following day by his family. Grimes told ABC's "Good Morning America" he doesn't remember falling, only waking up in open ocean in the middle of the night.
"I came to, and I was in the water with no boat in sight," he told the program, adding that he had a couple drinks but wasn't drunk. Grimes did not respond to Insider's request for comment.
Grimes described the next 20 hours as a fight for his life. He said he spent much of that time treading water, fending off jellyfish and at least one finned creature he couldn't identify. He made it through the night and the next day, until night struck again. He tried eating objects that floated by, including a piece of bamboo, in order to maintain energy.
Finally, a ship spotted Grimes and notified the Coast Guard, which rescued him.
'The top end of the survival limit'
Gross said to have someone survive in open water the way Grimes did was extraordinarily uncommon, and for many people would likely be impossible.
"The Coast Guard has invested a lot of time in technology and training for search and rescue, so we have a lot of programs that help us determine how long somebody could physically stay - without flotation - how long they could stay on the surface, how long they could survive," Gross said. "This is definitely the top end of the survival limit."
Grimes told ABC he was always confident he would be rescued, and Gross said that attitude likely contributed to his ability to stay afloat that long. He said Grimes' "will to survive," "natural instinct," and his efforts at "self preservation," like trying to shout out to rescue boats or reach offshore oil platforms, was "just not common."
Cat Bigney, a survival expert who has consulted for Bear Grylls and National Geographic, previously told Insider that simply keeping your cool in life-or-death situations could ultimately save you: "The biggest thing that will kill you in a survival situation is to panic."
As for Grimes chewing on objects he could find floating by, Gross said he wasn't sure how much nutrition something that is out floating 20 miles off the coast in the middle of the ocean could give you, but said those "small wins" could've added up to help him keep going.
Gross said Grimes also made smart in-the-moment decisions, such as taking all of his clothing off so they would no longer weigh him down, making him more buoyant.
When Grimes was finally rescued, he was treated for shock, dehydration, and hypothermia - another severe risk factor when spending 20 hours in 70 degree water - but he was able to be released in a matter of days. Gross said the hypothermia could have been much more severe, but a number of factors can help curb it.
"It's so dependent on the person: the time they last ate, the body fat content, what they go in the water with, how comfortable they are in the water," he said, adding that whatever Grimes' particular circumstances were surely helped him avoid the worst of it.
The Coast Guard rescuers
By the time a Coast Guard rescue swimmer reached Grimes, he was just about at his limit. The rescuer, Richard Hoefle, an aviation survival technician, said he thought Grimes had just moments of energy left when he was rescued.
If the boat that spotted Grimes or the rescue helicopter were 10 or 15 minutes later, it's possible Grimes wouldn't have survived, Gross said, crediting that to the Coast Guard's robust search and rescue operations and efforts to maintain relationships with the boating community.
Cruise ship officials notified the Coast Guard of the man overboard situation at around 2:30 p.m. on Thanksgiving day - more than 14 hours since Grimes was last seen. After launching the search and rescue mission, the Coast Guard quickly sent out a broadcast to alert other mariners in the Gulf of Mexico that they were actively looking for someone in the water.
Crew aboard the bulk carrier vessel "Crinis" ultimately spotted Grimes, who had been waving and shouting to get their attention, and notified the Coast Guard of his location.
"I do think that is part of the reason that the motor vessel had that lookout and was able to report him to us," Gross said. "So that's just one of those puzzle pieces that really paid off in the end."
When the Coast Guard got the call, the rescue helicopter was only about six miles away from the area where Grimes had been spotted - another factor that allowed them to get to him and pull him out of the water quickly.
Gross said the helicopter's clutch location was thanks to the Coast Guard's Search and Rescue Optimal Planning System, which allows them to estimate where a floating object could be. The program essentially takes 5,000 virtual rubber ducks and drops them at a specific location in the ocean, Gross described. It factors in things like the person's weight, clothing, body fat percentage, and whether or not they have a flotation device, and projects where they could potentially float to in a specific amount of time, factoring in weather and ocean patterns.
"The highest concentration of those rubber ducks is where we would search first," Gross explained.
For Grimes, the system returned over 7,000 square nautical miles of ocean where he could potentially be - roughly the size of Massachusetts. But it was accurate enough to put the rescue helicopter in close vicinity to where he was ultimately found.
"It is pretty astounding," Gross said. "This is what we do on a day to day basis. I think one of the main reasons that people join the Coast Guard is to serve the American people in times of distress, exactly like this case."
"Then to have the outcome of us rescuing him is just a really, really incredible story of how it all comes together."