If a plunging wave is not parallel to the beach, the breaking section (or curl) will move laterally across the face of the wave. This is the "tube" that is so highly sought after by surfers (also called a "barrel", a "pit")

If a plunging wave is not parallel to the beach, the breaking section (or curl) will move laterally across the face of the wave. This is the "tube" that is so highly sought after by surfers (also called a "barrel", a "pit")