Liquisity is a problem-solving action game where the player must get a ball past obstacles into a goal. Each level is set underwater. The player is given a cannon which can be used to fire a ball, with varying force. Once a ball is launched, the player can control it to a limited degree, with the left and right arrow keys. If a ball is destroyed or goes offscreen, the player can launch another.
The levels contain obstacles and elements such as fans which block the way, sharp fans which destroy the ball, bubble jets which propel the ball in a specific direction, and others. Solving the level often involves carefully hitting switches to deactivate inconvenient obstacles. There are several different types of balls, in addition to the basic one: the metal ball is heavy and hard to control, but it can shatter glass barriers; the seltzer ball slowly dissolves in water and thus has a limited lifetime, but it can fit in tight spaces and avoid obstacles when shrunk, and it can be made to float upwards at any time. There is also a helicopter ball, which can move freely in any direction, but cannot exit the level.
The game includes a built-in level editor, as well as some unlockable bonus content.