Swell is the regular longer period waves generated by distant weather systems - think of a rock thrown in a pond, and you'll see swells. Waves & Swell are often used to mean the same thing .. in common language many like to think of "swell" as the regularly spaced lumps that approach your local surf spot, and "waves" as when they break/something to stick your surfboard on. Wave height (trough to crest) refers the average height of the highest one-third of the waves.