A man who fell off of a cruise ship in the middle of the night said he survived by treading water for 20 hours, eating bamboo, and fighting off jellyfish in shark-infested waters

• The man who tumbled off of the Carnival Valor cruise ship the day before Thanksgiving spoke out.

• In an interview with ABC's "Good Morning America," he described in detail the 20-hour fight for his life.

• Another passenger on the ship said that others were not notified about what happened.

A man who fell off of a cruise ship in the Gulf of Mexico after a few drinks shared his story of survival for the first time, describing how he trod water for almost a full day and fought off sea creatures while fading in and out of consciousness.

In an exclusive interview with ABC's "Good Morning America," passenger James Michael Grimes said he had a couple of drinks on the Carnival Valor on November 23, the night before Thanksgiving. He wasn't drunk, he said, but doesn't remember what happened next.

The next 20 hours of his life ended up being a fight for survival, he added.

Grimes shared with ABC that after telling his sister he was going to the bathroom at 11 p.m. local time that night, he regained consciousness in the ocean.

"I came to, and I was in the water with no boat in sight," Grimes told ABC. The cruise was headed from New Orleans to Cozumel, a Mexican island in the Caribbean, traveling through the Gulf of Mexico. For the next almost 20 hours, Grimes described how he trod water and fought for his life, encountering jellyfish and another unidentified sea creature with a fin.

"It came up on me really quick and I went under, and I could see it. And it wasn't a shark, I don't believe," Grimes said. "But it had more like a flat mouth, and it came up and bumped one of my legs, and I kicked it with the other leg. It scared me, not knowing what it was, all I could see was a fin."

As night struck and Grimes awaited rescue, he said that he had to eat objects floating by to sustain his energy, including a plank of bamboo.

"It gave some type of flavor in my mouth other than saltwater," Grimes told ABC. "I was never accepting that this is it — this is going to be the end of my life."