RedactedNarrative: Vessel 1 was approximately 2 miles off shore ocean side fishing with 5 occupants on board. The weather consisted of heavy winds and large swells. Witnesses say waves were crashing over stern of the vessel. Vessel began backing up into waves allowing for more waves to crash over stern and begin filling up the boat. The operator was unaware of the amount of water filling his vessel while backing up and then once realized called USCG who relayed the information to FWC. The vessel planed from Mosquito Bank to John Pennekamp State Park fuel docks where the vessel immediately sank after stopping causing all occupants to go into the water with life jackets on. USCG was following the vessel into John Pennekamp and everybody was rescued. Owner/operator stated bilge pump was working in the morning prior to fishing. Possible mechanical failure.  No injuries. Vessel totaled.