Matt Eggers said he was fishing along the river near the Hollywood Casino and I-275 Bridge when he heard a bang and saw a man on a nearby boat calling for help.
Within seconds, Eggers said the boat was engulfed in a massive fire.
Eggers told the boat's driver, Dakota Ball, to jump onto the front deck of his boat and the two backed away from the fire.
The Lawrenceburg Fire Department and Cincinnati Fire Department showed up and extinguished the fire, which had burned for around two hours.
Eggers said both he and Ball are doing OK.
He said it's a reminder to wear life jackets because things can go wrong so quickly.