Abstract: A buoyant capsule depth controller is presented for positioning and maintaining a capsule within the ocean waters for establishing an observation or defense station. A bouyant capsule is connected to a weight assembly by means of explosive fittings which detonate at a predetermined depth to separate the two. The buoyant capsule and weight assembly are then held together by means of a short line of fixed length until a second predetermined depth is reached, at which time a pressure-actuated release mechanism releases the short line and a cable wound within the weight assembly is payed out to the buoyant capsule below a preset depth as the weight assembly sinks to the ocean floor. The paying out of the cable rotates a shaft within the weight assembly which in turn drives an hydraulic pump, the output of the pump being controlled by a valve to regulate the amount of drag which the pump exerts upon the shaft thus controlling the rate of cable pay out.