Abstract: A vehicle or robot movable in the water includes a body having a first opening in its abdomen. A float is provided at the front portion of the body so that the vehicle body suspends in the water with its front portion up. A pressure reducing device is provided in the body for reducing an inner pressure of the body so as to cause the body to suctionally adhere on a wall in the water with its abdomen facing the wall. A sealing skirt is attached along the first opening formed in the abdomen so that it contacts the wall to maintain the body's inner pressure negative as the body adheres on the wall. A drive unit is also provided in the body for moving the body on the wall. The pressure reducing device includes a hose communicated with the body at its one end and a pump connected with the other end of the hose for pulling water out of the body.