You can see the four most common boat hull types in this simple drawing. If you have ever been on a flat-bottom boat and on a modern fishing boat, you know.
Boats with displacement hulls are limited to slower speeds. A round-bottomed This planing hull gives a smoother ride than a flat bottom hull in rough water.
The 'hull' is the portion of your boat that rides both in and on top of the water. Flat-bottom boats tend to be less stable than other hull types in rough water.