Four individuals were able to escape, what they said, was an explosion of their boat near Key Biscayne.
City of Miami Fire Rescue crews responded to the scene near the Marathon fueling station on the Rickenbacker Causeway at approximately 8:50 a.m., Wednesday.
Officials said four occupants were on a 21-foot boat when, they said, it exploded.
The four individuals were able to swim back to the dock.
One of the boaters was transported to Mercy Hospital in stable condition with a laceration on his foot.
7SkyForce HD hovered over the scene where officials could be seen investigating in the water.
The vessel is no longer on fire but remains in the water.