There are three main classifications of hulls; displacement, semi-displacement and planing.
A hull type is named according to its shape, particularly the shape of the hull's run.
This shape affects the vessels general performance and ability to attain certain
speeds. Therefore, a vessels with equivalent displacement and the water line length, depending on hull shape, may attain very different speeds and levels of efficiency.
At displacement speeds a planing hull performs the same as a displacement hull,
in that; its full weight is pushing the water aside but a planing hull’s transom
separates abruptly from the water flow so that when planing it does not incur negative
lift but at displacement speeds it creates additional turbulence thus making the
hull less efficient at displacement speeds. A displacement hull on the other hand
is limited by its hull speed whereas a planing hull is not. These hull types consequently
require different propellers and amounts of power for optimum performance.