The Martin County Sheriff's Office said the wild scene unfolded Friday after three men said they were doing a "photo shoot" aboard the 24-foot vessel in the St. Lucie River when they somehow fell overboard.
The incident unfolded in the late-afternoon just south of the Stuart Causeway in Stuart.
After the group of men fell out of the boat, the unmanned vessel continued to circle them as they tried to stay afloat in the river.
"The three male occupants told MCSO marine deputies that they were forced to dive underwater numerous times because the boat continued to circle around, nearly running them over," the sheriff's office said.
The out-of-control vessel eventually straightened itself out - then traveled at a "high rate of speed," racing toward a concrete dock near the 1500 block of St. Lucie Boulevard in Stuart.
Footage released by the sheriff's office shows the boat hitting the dock, going airborne, and then coming to rest after smashing into another dock.
"MCSO Air-1 Pilot Justin Lundsteadt stayed over the vessel to direct marine units to the passengers. Meanwhile, Chief Pilot, Deputy Doug Newsom captured this unbelievable video," the sheriff's office said.
The three men were able to swim to a nearby sailboat and avoided serious injuries.
"One of the men suffered minor injuries," the sheriff's office said.
An investigation into the cause of the incident was turned over to the Florida Fish and Wildlife Conservation Commission, which investigates boating accidents.