This swimming hole literally gets a million+ visitors per year, but it’s for good reason. The 10,000 acre state park offers sandy beaches on each end of the lake. Or you can paddle to your swimming spot in the middle of the lake (you can rent boats at the park concession stand). Only electric motors are allowed on fishing boats. Plus, if you bike into the park, admission is free.
As a bonus, there are several great hikes with amazing vistas and toprope climbing spots as well.