Factual error: In the series, Columbo does not carry a gun, and in several episodes it is mentioned that he doesn't like guns and/or that he doesn't know very much about them. In the real world, all LAPD officers must carry guns, and they must re-qualify with them at the range six times each year. Also, due to the very nature of their work, they are knowledgeable about numerous types, makes, and models of guns.
Factual error: Devlin proclaims himself to be a staunch Irish Republican but he refers to the Northern Irish city of Derry as "Londonderry." This is the name imposed upon the place by the British and is despised and rejected by Republicans. Devlin would refer to the city as "Derry."
Trivia: Peter Falk's real-life wife appeared in 6 episodes, each time as a different character.
Any Old Port in a Storm - S3-E2
Question: As a homicide detective, why would Columbo have been present at an apparent drowning incident?
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.
KeyZOid
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."
KeyZOid