Twelvemile Beach or Hurricane River are both nice if you want to be right in PRNL. Not too far to the south are the state forest campgrounds of the Gemini Lakes, Ross Lake & Cusino Lake... we used to like Cusino because it's a little more remote and only has like six sites... quiet.
East of Grand Marais about 20 mi. is Muskollange Lake State Park... also used to enjoy that quite a bit. Muskollange Lk is an inland lake and Lake Superior is right across the road.