Abstract: A swimming pool mounted externally of a floating ship or barge. A rectangular horizontal frame supports a walkway about an open rectangular area. A first outer net extending from below the outer borders of the walkway is mounted to telescopic vertical supports that are driven by gear motors to raise or lower the first net, and a second inner net extending from below the inner borders of the walkway is fixed about rollers suspended from the frame, with gear motors linked to the rollers to elevate or lower the second net by winding or unwinding the second net upon the rollers.