There is no Norm

"Conditions vary greatly and the speed, shape, cadence, and height with which the seas crash onward to the land in violent crescendo are largely governed by the great compressive influence of bottom contour, bottom declivity, and bottom channels.

The truth is that there is no norm. Safety and success in running broken surf depends almost wholly on the individual captain's brand of seamanship as suited to the particular hull under him."

-- Charles Frederic Chapman, from Piloting, Seamanship, and Small Boat Handling