The game is a side-scrolling platform game played as the hippopotamus Hipopo, who travels through the land of Woody Lake throwing water bombs (called "mizubaku") and rescuing other hippos. The water bombs are primarily used to soak and disable enemies, but they can also extinguish fire (which is frequently used by enemies as an attack), water plants to cause them to grow (so they can be used as platforms), and make watermills and other mechanical devices move. Outdoor levels start in daylight but get darker as time passes. There are numerous hidden rooms throughout the rounds. There is a two-player alternating mode where players take turns.

The English patch was released in late 2026.