Training a Dog Not to Go Pee in the Lake?

We just moved to a lake house and my Lab has gotten into the habit of going into the lake to pee. Any idea how I can stop this behavior? I am not thrilled. She is doing this for obvious reasons. But in addition to that, she is getting a rash on the groin and belly area from being wet so often. I towel her every time she comes in, and the laundry, ugh! Any ideas, besides moving?

By rob