are both primarily generated by wind or wind events like storms.

Wind waves refers to waves that are being generated by the wind in the same area as the waves. TCSurfski Description of Wind Waves

Swell refers to waves that have moved beyond the area of wind that generated them, sometimes traveling great distances and not “affected” by the local wind (the swell retains its size and speed - although it can be masked or made less visually obvious by large local wind waves). Swell waves tend to be longer and faster than local wind waves. “Groundswell”or “ground swell” refers to swell that has traveled 1000's of miles and is often identified by a period (time between waves) of more than 15 seconds.

Larger Waves (including Freak Waves, and Seiches) - wave size increase happens when:

• Wind puts pressure against strong ocean current
• Ocean depth change is dramatic
• Two close storms cause overlapping waves

when waves roll over shallower areas such as shorelines (Shore Break) the deeper part of the wave slows due to friction from the underlying shallows while the tops of waves keep their speed and eventually topple over (break). This process can occur anywhere (not just close to shore) there are shallows due to features such as underwater reefs, shallow bottom shelves, and sand bars. Very shallow water will cause all waves to break which is usually easy to notice, while deeper shallows will cause only bigger waves (Boomers) to break sometimes with periods of 30 minutes or more between breaking waves. Such breaking waves can be surprising (particularly for paddlers unfamiliar with the underlying shallows) and have to be watched out for carefully by folks in smaller vessels. The indigenous Australian term for areas with large offshore breaking seas due to reefs and shallows is Bombora. Nautical charts are available online (view or download) for coastal waters around the world to allow anticipation of shallows and potential boomers, although online viewers may not have sufficient resolution to show all smaller shallow areas. Water depth and resultant occurence of breaking waves can also vary with the tide.

flat shorelines usually absorb most wave energy while steep shorelines and barriers in the water can cause waves to bounce off and rebound with the rebounding waves working at odd angles to the prevailing wave patterns and causing greater turbulence. This can create more challenging paddling. It also can contradict the usual wisdom of staying closer to shore for safety or easier paddling when rebound makes for more difficult paddling conditions closer to shore. Transient rebound can quickly cause more turbulence when larger waves from passing boats or ships bounce off of the shore. Abrupt barriers in the water can cause pronounced rebound referred to as “clapotis”. If a steep shoreline is shallow enough to expose flat shore at lower tide levels then wave energy will be better absorbed and rebound can be mitigated during lower tide.

Rebound Videos

If you have access to a shipping channel or some water where there is large boat or ship traffic, be aware of the interaction between water depth and boat wakes (refer to “breaking waves” above) and where it is better to position yourself. Shallower water can cause boat wakes (like all waves) to steepen and possibly break. This may be good for surfing where it allows you to more easily catch boat wakes (particularly from smaller boats) if they get somewhat bigger and steeper, or it can make already good size wakes too big, too steep, breaking, and more dangerous than you want to deal with.

• Where to Find Boat Wakes
• Boat Wake Riding Videos
• Surfski.info Discussion On Riding Boat Wakes 4/2018