A 28-foot boat exploded with six occupants on board at the Lauderdale Marina.
William Garland, a retired firefighter, was nearby and immediately helped to render aid.
"It blew the back of the boat to pieces," Garland said.
The boat was backing into a fuel dock at the time of the explosion.
One adult was taken to Broward Health Medical Center with serious but not life-threatening injuries.
Three others, including a second adult and a minor, were also hospitalized with minor injuries.
"It was a flash explosion," Garland said. "The flames were hot instantaneously and then they went out. It could have been much worse if this thing would have caught fire."
Garland said a 30-year-old woman suffered a fracture to her left leg.
"Her son was about 5 years old and he had just singe burns on him," Garland said. "Because the explosion blew the fire out, thank God for that. So all we did was tend to the injuries."
The cause of the explosion remains under investigation.