If, within a vertically circulating-type test tank’s closed water course, some water velocity is generated, using the impeller and if a test body is fixed in the water flow, the force exerted on the body can be measured and the flow around the body can be observed. After being adopted in 1985, not only hull shape development but also a variety of tests were conducted and a high operating rate has been achieved. Many of Tsuneishi Shipbuilding’s products and technologies were borne out of this water tank.