Groco AS-100 bilge switch turns bilge pump off and on by sensing changes in pressure (caused by rising or falling bilge water level) in its air tube.  No floats to stick or fill with water.

Approximate levels are "ON" at 7 cm (2-3/4") of bilge level and "OFF" at 2.5 cm (1").  Use with a pump that draws up to 10 A running continuously or up to 20 A running intermittently.