Abstract: A signaling means to indicate levels in a liquid receiving compartment of a watercraft. The compartment contains a float which is connected to a piston by a vertical piston rod. The piston rises in a cylinder when the float rises in response to admission of liquid into the compartment whereby the piston effects two timely spaced compressions of a confined gas which actuates a pilot valve for a flow regulating valve when the pressure of confined gas reaches a preselected value. The regulating valve then admits compressed air to a device which furnishes visible signals and to a device which furnishes audible signals. The first set of signals warns the attendant that the compartment is about to be filed, and the second set of signals informs the attendant that the compartment is full. The attendant then closes a shutoff valve in the pipe which admits liquid into the compartment, and this results in automatic reduction of the pressure of confined gas.