The dialogue between Sgt. Kramer and Lt. Columbo over smoking (Kramer: "Thought you were gonna quit;" Columbo: "Not yet. No, not yet, Sergeant. Not yet") as Columbo figuratively rides off into the sunset (actually, rowing himself away toward a yacht club), is almost certainly a clever response directly aimed toward intense fan curiosity at the end of season five over Peter Falk returning to play Columbo in subsequent years.
This episode was directed by Patrick McGoohan, who also holds the record for appearing as a murderer on the series on 4 separate occasions over the years.
When the series was resurrected in the 1990s, Columbo states that he has never driven his car with the top down. But he does in this one, presumably so that the five people can cram into the small car before they drive off. Columbo first had the top down on his Peugeot 403 in Season 1, episode 2 "Lady in Waiting"
The Commodore who is murdered is named Otis Swanson. In (The Case of the Dead Ringer (1966)), the murder victim is also named Otis Swanson. Jackson Gillis is credited as the writer in that episode as well as this one.
This is the only Columbo episode in which the audience does not know the murderer from the start. Contrary to the normal Columbo "howcatchem" plot, this has the classic "whodunit" ending scene with all suspects gathered in a room to reveal the perpetrator, in much the same way as Hercule Poirot gathers the suspects. This could be a nod to the great mystery writer, and queen of "whodunnits", Agatha Christie.