The S3 level sensor is most common used in Marin application for fuel and water level measurement. S3 is preferred because of its simple, but solid construction. The reed switch technology gives  you sufficient resolution down to 7 mm, standard is 21mm.

•    Stainless steel 316 or 304
•    Standard lengths from 150 to 2000mm, longer sensors available upon request
•    IP 67
•    BSP 1 ¼ treads
•    Available with many different connectors upon request
•    European Ohm standard 0-190, US Ohm standard 240-30.
•    Available also with 0-20mA, 0.5-4.5 VDC and 0-5 VDC
•    Operating temperature -40 to +85 Celcius