Understand what swell period means and how it affects wave quality.
Swell period (wave interval) is the time between successive wave crests. Short periods (4-8s) are windswell - generated locally by wind, messy and close together. Long periods (12-20s) are groundswell - generated far offshore, powerful and well-spaced. Wave energy grows with period, so a 2m swell at 14 seconds has roughly 4x the energy of a 2m swell at 7 seconds.