Abstract: The invention is a bi-level fluid level sensor intended to be used in the bilges of boats with complementary equipment which activates emergency equipment such as warning devices and/or pumps when the upper level is reached, and deactivates such equipment when the lower level is reached. The sensor is uniquely constructed of three specially coatedwater repellent probe elements which are received in a socket which is in turn imbedded in a molded body of plastic or the like to absolutely seal the sensing unit against corrosion and mitigate against the accidental bridging of the probes by oil slicks and bilge slime.