Crest

The crest is the highest point of a wave profile or, by extension, of a ridge, sitting above the still-water level where the surface is convex upward. For a surface gravity wave the crest is where particle orbital motion runs forward in the direction of travel and where elevation, hence runup and overtopping potential, is greatest. It pairs with the trough, the lowest point; crest-to-trough is the wave height, and crest-to-crest is the wavelength. As a wave shoals the crest peaks and narrows while the trough broadens, the profile leaving the symmetric Airy shape, until the crest plunges or spills when its forward speed matches the wave celerity.