Present deep submersible powerplants are limited in terms of on-board energy storage capacity. Of the planned advanced deep submersibles, the Deep Submergence Search Vehicle (DSSV) is an immediate and typical advanced power system application. This paper discusses DSSV power requirements and briefly outlines and compares the competing power system candidates. The pressure balanced, hydrazine-hydrogen peroxide fuel cell is identified as a leading competitor. A typical system approach is described, system design options identified, and system advantages cited.