Possibilities: Destruction of evidence  of human trafficking.  Vessel could be carrying contraband that it did not want discovered.  Evidence of toxic waste consumed by fire.  Chemicals used in the production of methamphetamine, highly flammable, drug of choice of the persons unlawfully in the State.  Possibility of human remains not wanted discovered,   Possibilities are endless.  Boat just don't burn especially when watched during a salvage operation.