When referring to types of boats, the deep vee describes the height of the boat's side walls. There are shallow vee boats which have short sides, and deep vee boats which have taller or deeper sides. The benefits of a deep vee boat lie in its ability to navigate through rougher seas without water swamping the boat's occupants or cargo.
Deep vee hulls will typically run deeper in the water than a shallow vee or a flat-bottom boat, and are therefore used in bigger or deeper waters. The design is found in fishing boats, as well as military ships. In these cases, the craft is subjected to a vast array of differing seas and must operate well, even in foul weather.
Many small boats that operate on inland lakes are deep vee designs. This allows the boat to take on larger waves, and can be much more stable for a novice operator. Riverboats are most often shallow vee or flat-bottom designs; however, in the larger and deeper rivers, deep vee boats can also be found.
By design, a deep vee boat will require a bit more horsepower to push it through the water. The shape of the hull allows more of the craft to sit below the waterline, which results in the motor working harder to push more of the ship through the water. Sitting below the waterline, deep vee hulls usually ride much more smoothly through rough water than a shallow vee or flat bottom boat. Boats with the latter design will ride on top of the rough surface of the water, while the the deeper vee-shaped hull will slice through the waves and remain more stable.
Many of the world's top off-shore powerboat racers rely on a deep vee design for their racing craft. By allowing the boat to slice through the waves instead of skipping across the top of the water, the boat is much more controllable. It is also less prone to damage, requiring fewer repairs.
By keeping the boat in the water longer between waves, the engine's propellers are also kept in the water more, resulting in more stable power and speed. In rough seas, this is extremely helpful. In smooth flat water, the engines can be tuned for greater horsepower, and the boat can be trimmed to hold it higher in the water, resulting in a very fast craft in any type of water.
Many fishermen enjoy the deeper hull for its added safety benefits. By having taller sides, younger children are less likely to fall over the side. This design makes a nice boat option for families who enjoy angling.