Boats come in a wide variety of shapes and sizes—and so do their hulls. Despite the variety, all hulls are designed to do one of only two things: either displace water, or ride on top of it, which is called planing.
Sailing boats, slow-moving boats, and large boats like cruise ships have displacement hulls. The combination of their weight and power means they move lower in the water, pushing or displacing water, rather than riding on top of it.
Smaller, faster boats, like powerboats or personal watercraft, typically have planing hulls. Planing hulls are designed to rise up and ride on top of the water at higher speeds.
Now let's look at some specific hull types.
There are four common types of boat hulls.
Boats with "flat-bottomed" hulls are very stable, great for fishing and other uses on calm, small bodies of water.
"Round-bottomed" hulls are typically displacement hulls, and are designed to move smoothly through the water with little effort. An example of a round-bottomed hull is that found on a canoe. One drawback to the round-bottomed design is that it's less stable in the water and can capsize more easily. So, extra care needs to be taken when entering, exiting and loading these types of boats.
"V-shaped" hulls are planing hulls, and are the most common type of hull for powerboats. Deep v-shaped boats are designed to plane on top of the water at higher speeds and provide a smoother ride through choppy water. These boats are usually equipped with a larger engine than flat or round-bottomed boats.
Finally, let's look at "multi-hulled" boats. These boats can have either planing or displacement hulls depending on the shape of hull and size of engine. Multi-hulled boats are some of the most stable on the water. They also require more room to steer and turn. Examples of common multi-hulled boats are catamarans and pontoon boats.