Swells form into a regular pattern of larger and smaller groups of waves. The largest waves in this pattern are called sets, and the smaller waves are referred to as lulls. The number of waves in a set and the duration of the lull between sets is generally consistent within a given swell but varies between swells.
From one set to the next, waves in the set are generally consistent in their size relationship. In a three-wave set, for example, the size relationship may be as follows:
- smallest
- medium
- largest
A lifesaver can avoid negotiating larger set waves and get out to sea more easily (and faster) by timing the lull and using the rip current, which can flow faster, or ‘pulse’, following a set.