Lunch on the lake????
Waterfront, next to Smokeys Musky Shop and launch is a nice option. Decent burgers, great pizza and wings.
Arguably the best pizza in the area is the Drydock on the north side of the lake. I've known people to pick up a pie and eat it in the boat when out there.
I think the best burger in Waukesha county is found at the Sportsdoc on the south shore of the lake. Right next to it is the SandBar which I'm told has good food, too.
All of those places have piers to tie up and grab your food.
But if you are coming to the lake, the BP on the corner of G and Prospect has great pre-made sub sandwiches in their store.
Enjoy your time on the water!
Used to be places on Nagawicka but it has been 20 years since I've been on that lake so don't quote me.