This is a huge area with several lakes created from a former sand quarry. It's a place of contrasts, so what you get depends on where you go.
If you're looking for a natural swimming spot and don't mind a bit of an adventure, the newer lakes here can be quite nice with clean water. The sheer size of the place means you can usually find a private spot for yourself, whether it's a small sandy beach or a grassy patch among the reeds. It's also a very popular spot for fishermen, with some big catches reported. Plus, there are spots where you can make a campfire.
Be warned, the access road is in really bad shape. Many of the older lakes are not great for swimming, with reviewers complaining about green, smelly, and muddy water. It can also get a bit crowded with campers and anglers who sometimes drive their cars and even trucks right up to the shore.