RedactedNarrative: Due to weather conditions and seas the waves began to flood over the stern.  Operator went to energize the bilge pump to de water the bilge space but found it to be inoperable.  Operator and one of the passengers jumped overboard to try and swim the vessel to the beach but the vessel keep filling up with water and eventually flipped over.  Officer examined the vessel and noticed the boat plug on the transom was missing.  If the plug were missing or installed incorrectly flooding would result in the vessels bilge area.