Abstract: A plastic paddle is pivotally connected to the operating arm of a microswitch. The paddle is positioned in front of a boat's drain opening. The paddle can be swivelled to one side to allow removal of the boat's drain plug. When the plug is removed and the paddle lies in front of the drain opening, if the boat is launched without replacing the drain plug, the inrushing water will move the paddle so as to close the microswitch and actuate an alarm. Enough of the drain hole is left uncovered by the paddle to allow water to drain out of the boat.