Im Wannseebad.

IMDb categorises this early German film as a documentary, but given its opening and closing shots, in which we see a small, buffoonish cameraman clowning around, it could also qualify as a comedy. The film is about five minutes long, and sandwiched between these aforementioned shots we see a collection of scenes of bathers on a beach. The majority of them grin at the camera like loons and follow it around like filings attracted to a magnet. (imdb)