A method of testing the electric field recording of a marine electromagnetic sensor cable including electrodes is provided. The method includes causing time varying current to flow between at least one pair of current electrodes disposed along the marine electromagnetic sensor cable. The flow of current generates a voltage in a body of water, thereby causing a secondary field impressed on a pair of sensor electrodes disposed along the marine electromagnetic sensor cable. A potential difference between the pair of sensor electrodes is measured. Accuracy of the electric field recording is inferred from the measured potential difference.