Wetrix is an unusual puzzle game that has you building up a 3D landscape in order to catch water that rains down from the sky. Each game begins with a flat area of land floating in the middle of the screen. Unless you build raised edges to store the impending water, represented by groups of bubbles, the resulting liquid will trickle down the area's edges and gradually fill a vertical meter called the drain. If too much water spills off the playing area, the drain will overflow and end the game.
Gameplay involves quickly finding a spot for each piece or object that appears at the top of the screen. Walls are created by rotating and dropping randomly shaped pieces, while the landscape is instantly raised or lowered by positioning pieces called "uppers" and "downers." Fireballs evaporate water, bombs create dangerous holes, and ice cubes freeze water for a short time. In addition to positioning pieces, you'll have to watch out for various dangers, such as devastating earthquakes that trigger when there's too much land on the playing field.
Bonus points are awarded for creating multiple lakes, generating rainbows by reaching a certain water volume, or having rubber duckies appear whenever a lake reaches a certain depth. In addition to the single-player mode, you can compete head-to-head against a friend via split-screen display. Other options include a challenge mode, where you have to work your way out of several scenarios, a practice mode that shows you how to use each piece, and a handicap option that lets you adjust certain parameters. High scores can be saved directly to the cartridge or via Controller Pak accessory.