In contrast to marine electrical cables routed throughout a ship, the undersea cable usually is required to carry heavy loads placed on the ocean floor or held in suspension from the surface. The paper describes various undersea applications from helicopter borne sonar systems to bottom layed acoustical and instrument arrays. Problems of materials selection for proper physical strength, reeling (fatigue) strength, corrosion, and torque balance are discussed. Various classical cable constructions are reviewed as options, accompanied with advantages and disadvantages for typical undersea systems.