Wind-generated waves that have traveled out of their source region, usually over a considerable distance. Swell waves exhibit a more regular and longer period with flatter crests than choppy, locally generated wind waves
National Oceanic and Atmospheric Administration's NOAA, Glossary of Some Terms Related to Rip Currents, U.S. Department of Commerce, Office of Climate, Water, and Weather Services, Silver Spring, MD, USA 2012. http://www.srh.noaa.gov/ripcurrents/glossary.shtml , (ND/ Rip Currents - Amer) {835}