In the opening river raft scene, the wide shot shows that at least one of the three men is wearing a life jacket. However in the three closeups of each man, none of them is wearing a life vest.
Early in the episode (approximately 12 minutes in), the deceased's family is in Perry Mason's office discussing his will. Paul enters wearing a light-colored jacket. In the next shot, Paul approaches Perry's desk wearing a clearly different, darker jacket.
(At about 21:00 min) The eye of the "dead" murder victim twitches in closeup.
When the search for the lost men begins, viewers see a TV broadcast covering it. The newsman states that "Air Force helicopters are searching for the missing men", but the chopper seen is clearly marked "US COAST GUARD".