Right, this is gunna be tricky but would really appreciate any help.

im think maybe 70s-80s film, and all I kinda remember is a kid/possible teen, trying to swim to a bank away from something (possible shark or sea monster) and there’s someone on the bank calling them and trying to help, think it has something to with treasure and I can remember seeing a vintage bubblegum wrapper too. I’ve literally been struggling with this for years