Take a kayaking trip on the lake. Just be sure to not use a whitewater kayak to do that. I had a wonderful idea to paddle down the whitewater river until it dumped into the lake. Only one problem, I didn't realize that I was going to be paddling 2 miles in the flat lake water with a flat bottom white water kayak. I believe I completed an Olympic workout after I made it back to the truck.
"> Kayaking across a lake with a whitewater kayak is work.