Tarza Water Park is a large family-oriented water park in the Dededo area, one of the main non-beach recreational facilities on Guam. It has wave pools, water slides of varying intensity, and a lazy river. The park is popular with local families and with Japanese tourists — Guam receives a large number of Japanese visitors and the park's marketing reflects this.
It is not a destination in itself for most independent travellers, but if you are travelling with children or want a day away from the sea, it serves the purpose. Prices are lower than comparable parks in the continental US, and the crowds are manageable outside school holidays. The on-site food is basic and overpriced; bring your own snacks if you can.