Music in the film

Hi. I recall (when I was young) seeing a film (1970s?) with some guy (and a girl?) sinking in the water with 'concrete shoes'... and since then have been trying to figure out what film it was. Couldn't figure it out for the many years, but recently someone pointed me to this film. It looks like this very well may be it, though I haven't managed to find any clips or info to verify it.

The sequence in question, seemed to be part of the end titles (though I may be wrong).... and I seem to remember some music, which was a sort of mellow 'ragtime' style song (upright piano?) with a guy whistling the lead. I think there was a guy and a girl underwater, though that's about all I remember.

I was wondering if anyone familiar with the film could verify that what I am describing is in this film.

Many thanks in advance!