Ship squat is the averall decrease in the static underkeel clearance, forward or aft, created by dynamical sinking of a ship when moving ahead. When a ship proceeds through water, she pushes water ahead her. In order not to have a “hole” in the water, this volume of water must return down the sides and under the bottom of the ship. The steamlines of return flow are speeded up under the ship. This causes a drop in the pressure, resulting in the ship dropping vertically in the water.