When young I went north to Redgranite WI a few times to scuba dive. The water was clear even in mid summer, but cold if you went beneath the thermocline. It was a flooded granite quarry 100 feet deep. We would adjust our buoyancy, no air tanks, then swim down 10 feet to a ledge, grab a rock and see how far we could go before we let go. I made it to 40 ft. We needed a cold water hood in July.
https://youtu.be/XeUr4urpGmchttps://youtu.be/7ccklES0kTwDevils Lake is also good for diving and many other things. Hiking is excellent. Camping.
https://youtu.be/1Zbq-54pmFMhttps://youtu.be/CZiH_UsQ1FAAnyone driving down to Madison or Chicago should take a 1 hour detour and take the Merrimac Ferry. Kids will never forget it.
https://youtu.be/uBmI3F3FOSs