So what is a swell? Even on the calmest days, storms raging elsewhere on the ocean create rolling waves that radiate away from the storm. These are called swells, and they can increase as storms intensify and near the coast.
A reported 10 foot swell means the water rolls up 5 feet above the flat level, and then the other side's base is 5 feet lower making for a total of a 10-foot swell.
Wind waves are, as the name suggests, the waves that are caused by current winds. A 3-4 foot wind wave would be on top of the current swell.
Some swells can reach over 30 feet along the Washington coast in the winter time when a strong storm is in the area.