RedactedNarrative: Operator of vessel reported a mechanical failure and taking on water earlier that day.  Sea Tow towed the vessel to a storage float for inspection.  The operator inspected the engine compartment and noticed the the battery was submerged and sizzling.  The operator closed the compartment cover and the vessel exploded.  Operator was ejected into the water and suffered multiple burn injuries.  Vessel sustained extensive burn damage.