Character mistake: Columbo took the Beretta off the gun display by inserting a pencil into the barrel of the gun. In a previous episode, he said to NEVER insert a pencil there because it will ruin the groove of the barrel, making it impossible for ballistics to get a match on the bulletin. When using a pencil, Columbo picks up a gun up near the trigger.
Continuity mistake: Columbo stops Mr. Finch on the road after following him from Biltmore hotel; as Columbo is speaking with him, the cigar in Columbo's hand is always in Finch's shot, even after we see Columbo place his hand on the roof. Plus after we see him put his hand down, the cigar ash keeps going from 1" to nothing. (01:44:20)
Other mistake: In the home of a murder victim, Columbo presses the telephone's "redial" button to see who was called most recently. A seven-digit number is displayed but only six beeps are heard as the number is redialed. Later, attorney Oscar Finch places a call by dialing only five numbers.
Continuity mistake: At the end, when Columbo is demonstrating on the mannequin, his cigar changes position between shots.
Answer: "Apparent" drowning answers your question - things are not always as they seem. Drowning could be accidental, but it could also be a murder in disguise. Moreover, the actual cause of death has not yet been determined - accident, suicide, murder, or natural cause (e.g, heart attack while swimming). Columbo would be there to investigate if anything looks unusual for it to be a mere drowning or if there is evidence or suspicion of something else.
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This was just on TMZ.com's "Aaron Carter Dead at 34" (11/05/2022): "Law enforcement sources tell TMZ... homicide detectives have been dispatched to the scene but we have no information or evidence of foul play. It's standard operating procedure for homicide detectives to investigate such [drowning] death scenes."
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