This is likely an obscure movie, since my only exposure to it was in the graveyard of afternoon weekday movies some time in the 1980s.
It was a comedy movie about some kind of crime that went wrong. I have a feeling that criminals were fumbling and foiling their own plans, but don’t quote me on it. It might have been something like a jewel heist or chase.
Anyway, the only detail I do remember is that the movie opened with a cast member (an established comedian, I think) standing on the beach, giving a to-camera intro imploring audiences to remember that the events were all true, and that they really happened.