When a body is submerged in water, it experiences a pressure acting normal to its surface and distributed over its area. For better structural design, it is important to determine the magnitude and position of the resultant force acting on the surface. Consider a rectangular plate of constant width submerged in water. As the pressure increases with depth, it results in a trapezoidal pressure distribution that varies linearly from the upper to the lower edge. The resultant force on this plate is due to the trapezoidal volume of water having specific weight. The line of action of the resultant force passes through the centroid of this volume. The point at which this line crosses the plate is called the center of pressure. Due to the constant width of the plate, the loading distribution can be represented in two dimensions. The resultant force acting on the entire plate can be expressed as the product of the trapezoidal area and the width of the plate.