delmarva now "A lot of factors contribute to the quality of a wave." by Roy Harrell
'Take sandbars for instance. You can't really see them, but you can see the effect of them. Waves come out of deep water and hit a sandbar and the resulting drag on the bottom of the wave causes the lip to pitch. How deep the water is and the steepness of the incline of the sandbar are determining factors in how hollow the wave will be.
'While it's impossible to discuss all the variables of bathymetry here and it's effect on waves, suffice it to say that in our area surf breaks are in a constant state of flux due to the fact that they're sand-bottom breaks. At many other surf spots around the world, the waves break on reefs or points. There may be some sand migration that affects the quality, but the underlying rigidity of the reef will keep the location of the peak stable and the wave will break more or less the same year after year.'