A marine electromagnetic sensor cable system, comprising a first sensor cable subsystem comprising: at least a first sensor cable segment comprising: a first termination plate disposed at a first longitudinal end of the first sensor cable segment, and a second termination plate disposed at a second longitudinal end of the first sensor cable segment, wherein each said termination plate comprises electrical connectors for making electrical connection to an adjacent sensor cable segment or to a signal processing module; a first plurality of spaced apart electrodes (E1-E4) positioned along the first sensor cable segment to electrically contact a body of water when the first sensor cable segment is immersed therein, and a first plurality of electrical conductors (36, 38, 40, 42), each of the first plurality of electrical conductors extending from one longitudinal end of the first sensor cable segment to the other to connect with the electrical connectors in each of the termination plates; wherein each of the first plurality of spaced apart electrodes is respectively coupled to a different conductor from the first plurality of electrical conductors; and a first signal processing module electrically coupled to the plurality of electrical connectors at the first or second longitudinal end, the signal processing module including a first voltage measuring circuit electrically connected to two or more electrodes from the first plurality of electrodes (E1-E4) at least a first sensor cable segment comprising: a first termination plate disposed at a first longitudinal end of the first sensor cable segment, and a second termination plate disposed at a second longitudinal end of the first sensor cable segment, wherein each said termination plate comprises electrical connectors for making electrical connection to an adjacent sensor cable segment or to a signal processing module; a first plurality of spaced apart electrodes (E1-E4) positioned along the first sensor cable segment to electrically contact a body of water when the first sensor cable segment is immersed therein, and a first plurality of electrical conductors (36, 38, 40, 42), each of the first plurality of electrical conductors extending from one longitudinal end of the first sensor cable segment to the other to connect with the electrical connectors in each of the termination plates; wherein each of the first plurality of spaced apart electrodes is respectively coupled to a different conductor from the first plurality of electrical conductors; and a first termination plate disposed at a first longitudinal end of the first sensor cable segment, and a second termination plate disposed at a second longitudinal end of the first sensor cable segment, wherein each said termination plate comprises electrical connectors for making electrical connection to an adjacent sensor cable segment or to a signal processing module; a first plurality of spaced apart electrodes (E1-E4) positioned along the first sensor cable segment to electrically contact a body of water when the first sensor cable segment is immersed therein, and a first plurality of electrical conductors (36, 38, 40, 42), each of the first plurality of electrical conductors extending from one longitudinal end of the first sensor cable segment to the other to connect with the electrical connectors in each of the termination plates; wherein each of the first plurality of spaced apart electrodes is respectively coupled to a different conductor from the first plurality of electrical conductors; and a first signal processing module electrically coupled to the plurality of electrical connectors at the first or second longitudinal end, the signal processing module including a first voltage measuring circuit electrically connected to two or more electrodes from the first plurality of electrodes (E1-E4)