Not just the lake! Hiking too!
Sleeping Giant provincial park, which offers camping near Thunder Bay, Ontario is named after the fact that the hills in the distance seem to represent a sort of sleeping giant (you can imagine a head, a torse, and feet in the air though you might not unless someone else hadn't framed it for you that way).
I've never found swimming in Lake Superior to be all that great, partly because the lake is so huge (biggest in the world remember) and it can be very chilly, but at the peak of summer you could still do it quite comfortably. Other than the swimming though you will DEFINITELY want to explore the trails. Watch out for porcupines, but as you hike the numerous trails make sure to take your camera along with you.
I forgot mine often and have regreted it ever since as some of the most rewarding views of Lake Superior and the forested region nearby could be found at the end of the trails. Most of the trails are quite challenging, with few 'human' constructs like stairs to assist people with, so be sure to choose wisely, and according to your personal stamina and energy level. [more ]