A bow wave is the wave that forms at the bow of a boat when it moves through the water. As the bow wave spreas out, it defines the outer limits of a boat's wake. The size of the bow wave is a function of the speed of the boat, ocean waves, ocean depth, and the shape of the bow. A boat with a large draft and a blunt bow will produce a large wave, while boats that plane over the surface of the water or boats fitted with a bulbous bow will create smaller bow waves. Reducing the size of the bow wave is a major goal of naval architecture, as bow waves sap energy from the boat and reduce fuel economy; as well, large bow waves can damage shore facilities such as docks if a large boat sails past at high speed.