The Water plugin offers the ability to create water ripple effects on the screen. It can be used to draw dynamic rippling trails with the mouse. It also has a "rain" effect that creates the impression of random raindrops falling on the surface of a pond.
Drawing trails with the mouse
To begin drawing trails of ripples on the screen with the mouse, hold down <Control><Super> and move the mouse. The mouse will continue to draw trails for as long as the keys are held down.
The rain effect