RedactedNarrative: Deceased jumped out of v1 to retrieve v1 cover.  Deceased was not a very strong swimmer and was struggling in water with cover.  Passenger jumped into assist with cover and told deceased to float and return to v1.  Deceased was still struggling to float.  Deceased reached v1, but hand slipped while trying to grab v1 and deceased went under water not to surface again.  Law enforcement thinks deceased my have suffered a medical condition while in the water, but that is not confirmed.  Alcohol was not a factor.  No mention of pfd used or on vessel.