An alarm Abstract is provided for a bathtub and includes a method for attaching to a wall of the bathtub, one being a suction cup. A float assembly is supported by the alarm housing to engage the alarm system. To use the alarm apparatus of the invention in a bathtub, one of the three attachment methods is used to secure the housing to the wall of the bathtub. The float is adjusted to the desired height. Water is added to the bathtub, which turns a waterwheel, and when the water level lifts the float assembly a sufficient amount, the alarm system is activated and sounds a warning alarm. The alarm system includes a waterwheel that's is spinning, a thin flat plastic bar that is attached to the float. The float raises the thin plastic bar into the waterwheel thus making a loud clicking sound.