The landscape
you can’t see.
Before a wave reaches your board, it meets a whole world beneath the surface.
Illustrative depth contours. Not a map of Devereux and not a navigation chart.
Bathymetry: topography, underwater.
A bathymetric map describes the shape and depth of the seafloor. Its contours join points at equal depth. Close contours suggest a steeper slope; wider spacing suggests a gentler one.
Read the contours.
Imagine walking downhill underwater. Where would the bottom drop quickly? Where would a sandbar interrupt your path?
Follow the wave.
As waves enter shallower water, their speed and wavelength change. Different parts of a crest can slow at different rates, turning the wave through refraction.
A break is a relationship.
A sandbar, reef, or change in bottom slope can alter where waves steepen and break. Add swell direction and tide, and the same stretch of coast can behave differently. The contour map is a starting point for questions, not a complete surf prediction.