Researchers believe that, in places with irregular bathymetry like Scripps Canyon, the surfzone resembles an atmospheric weather system in miniature, with areas of varying pressure on the scale of hundreds of yards. Currents around Scripps are a function of wind and waves, but more important, of water moving from high-pressure zones where sea level is relatively high to low-pressure zones around them. The high-pressure zones are created by the highest breaking waves.

"There are areas where the waves are really big, where the surfers are, then you move 100 meters [328 feet] on either side and the waves are really little," said Steve Elgar, a senior scientist at Woods Hole Oceanographic Institution (WHOI).

The energy produces alongshore currents running parallel to the beach. Convergent flows sometimes collide to produce rip currents that rush back out to sea. Other times the flow is divergent and alongshore currents skirt away in opposite directions. Black´s, like all other beaches, experiences a transport of sand in the process. It is at the southern end of a littoral cell, a region of sedimentary circulation that extends north to Orange County´s Dana Point.

On most of the coastline, sand lost from one beach might fortify another to the south or north. In the case of Black´s, when sand falls into Scripps Canyon, it never comes back.