Marysville Pilchuck High School Pool is open some evenings for family swim. It costs I think $8 for an 1-1 1/2 hour swim. That doesn't sound like a very long time, but trust me, when you're chasing kids, it goes very slowly! There is a large pool with a large divider at about the 4' mark. On that side there is a basketball hoop. On the other side of the pool, they throw in inflatable inner tubes and noodles for kids to play on. They have a diving board but it's rarely open. There is also a small kiddie pool about 2' deep. They have a lot of floaty toys them dump in for the kids to play with. Some days when we go, the kiddie pool is nice and warm, other days, by the time the hour is up, my kids have blue lips. They have life jackets for the kids to use if you just ask. They have a sauna on the pool deck for ages 16+. Washington State law prohibits kids over five from being in the wrong gender locker room, something to think about before you go. You can bring your own lock to lock up your valuables.