A system and method is provided for identifying degrading electrodes (12) in a marine electromagnetic survey system (1). A system may comprise a sensor array (18) operable for use in a marine electromagnetic survey system (1), wherein the sensor array comprises a plurality of electrodes (12). The system may comprise a shunt resistor (42) connected to the electrodes (12) and a processor operable to vary a resistance of the shunt resistor in the presence of a voltage across the electrodes. A method for identifying degrading electrodes may comprise measuring an electric field in a body of water with a pair of electrodes, wherein a shunt resistor is connected between the pair of electrodes. The method may comprise varying a resistance of the shunt resistor. The method may comprise measuring a voltage across the shunt resistor while varying the resistance of the shunt resistor to obtain measured voltages for different shunt resistor values. The method may comprise comparing the measured voltages of the different shunt resistor values to calculate resistance of the pair of electrodes.