The ‘Ol Swimming Hole on Anderson Island is closed as of this writing due to issues around its popularity during this time of Covid concerns. Don’t take the kids to Anderson Island if you’re hoping to swim!
This is the beach at Lowell Johnson Park, and authorities have closed it, and are asking you not to visit the island right now.
You can read the official announcement here if you want.
If you need other options for swimming with the kids, I have a list of swimming lakes here. Deep Lake at Nolte State Park is a particular favorite, though readers warn you that it does get deep quickly, as its name suggests. The lake post also has a list of rivers and creeks for wading at the bottom.
You can also go to any number of Puget Sound beaches, although the water will be cold. Here is our list of favorite beach outings. This one is the ones where you can find sand!