Some methods of visualization of flow are applied to some simple models for investigating characteristics of form resistance of ships. In the case of low speed tests in the circulating tank, by making use of mass transfer of Indian ink, black ink and water colors painted on surface of models, photographes can be taken easily, showing fairly well limiting streamlines on surface of models. It is shown that bilge vortices of ship models observed by means of tuft-grid correspond to the two-dimensional ones observed by using an apparatus which simulates the secondary flow around the section of ship models.