Couple in Lake Attacked by Mountain Man With Chainsaw

by Dave
(Wales)

What is the film where a man strips in a lake and a brunette woman sees him from the shore, strips and gets into the lake as well?

The villain is tall with black hair and dumb. He wears a sleeveless red plaid shirt. He's very jealous and goes after the lake guy with his chainsaw. I think that the chainsaw scene was outside a bar, in the daytime.

I wish I had more, I really do. Any ideas? Thanks for reading and I truly hope someone out there knows this movie.