I decided to rate the local swimming holes in case you have not explored them yourself, or if you're looking for a sure thing and don't have the time to adventure from one to the next.
Square Lake:
My personal favorite.
Pluses- Lots of shade available with both grassy areas and picnic tables. The water goes deeper here than in most of the other swim areas, so it is still cool when the summer heat becomes more intense.
Minuses- The bathrooms are dark and musty, and there are lots of stairs down to the beach. If you have lots of kids or stuff to unload, you may get a work out in before your swim. If you need a level entrance, go to the boat landing and unload there. You will have to move your car back up to the car parking lot.
Big Marine:
Pluses- Sandy beach is pretty close to the parking, and shaded picnic areas are available. The facility is quite new, so the bathhouse has a cleaner feel to it than Square Lake's. There is a huge playground a short walk from the beach. It's very popular with the kids!
Minuses- Very limited shade, and the water is pretty shallow, so it isn't very refreshing in the late summer. The swimming area is not very large.
Aside from the shade issue, the minuses I listed may be positives for those with small children. I think that they would be a bit easier to watch at Big Marine with the smaller beach and the water depth.
Both beaches have warnings signs for chiggers or "swimmer's itch" Both provide outdoor showers in which you can rinse after a swim. I highly recommend rinsing as a precaution against swimmers itch. It's not something that you want to experience!
Both beaches are free if you have a Washington County park sticker ($25/yr), or they are $5 for a daily pass.
