What is it?
More rocker?
Higher angle of exit and entry?
Flatter hull?

All of the above but give some consideration to the following thoughts.
Match the hull to the wave shape you are interested in surfing. The faster the wave the longer the hull needs to be. There is a wave shape for every hull shape. If the nose is going under, raise the bow and take some volume out of the stern. Disengage the ends a bit if you want more control. Surf specific kayaks will look more like surf board bottoms.
Hope this is helpful.