They have a wading pool which you can dip your feet in and is great for kids to play in. There's a little pond with loads of ducks in by the reservoir but no other bodies of water, like lakes, that you can access.
I went up the tower and the views are great, the conservatory was really nice too with lots of exotic plants.

A short and very easy trail but nice if you bring a book or just want a breath of fresh air without hiking up a mountain!

Not too far from Capitol Hill link light rail station, just head up the main street then down roy street and you'll find the park on the right.