A dewatering system includes a selective calibrating sensor circuit configured to receive sensor readings from an electronic sensor, to determine if the electronic sensor is immersed in water, and to generate a control output signal accordingly. The selective calibrating sensor circuit periodically performs a self-calibration when the electronic sensor is not immersed in water to cancel the effect of potential contaminants deposited on the electronic sensor over its operating life. The selective calibrating sensor circuit inhibits calibration when the electronic sensor is immersed in water.