The TV news report I saw said the couple and their young son were on board, so unless one of them was the pilot there were actually 4 people on board. The dad said he was told they "lost an engine" so maybe only one side quit? Unless taking off or otherwise slow with full power it seems like that should have been controllable, esp since the aircam's engines don't look like they're mounted very far outboard. Unless the single engine just couldn't maintain altitude & they were so low that they descended into the water before the pilot could take any corrective measures.
Like they say, airspeed is life & altitude is life insurance.
minimums are for busting