If you want to see Buster Keaton in a beach movie, see "CONEY ISLAND (1917)" wherein he plays a lifeguard who gets the girl (in a stunning stripped bathing suit!) in the end.
Awesome pratfalls and stunts that probably inspired Jackie Chan! His pure physicality in his youth makes all the guys in the '60's "Beach" movies look like a bunch of wimps!
Even at the date of this movie he pulls a couple of impressive pratfalls - yeah, he rules.
shareOn a recent rewatch I briefly thought maybe they used a double for Keaton in the scene towards the end when the Rat Pack falls through the floor. Since the scene is slightly sped up you only see his character a split second (and from the side).
So I rewound it and paused and it indeed is Keaton. I know falling onto a mattress or whatever it's the hardest of stunts, but indeed it's impressive the 69 year old still had it in him.