Surf Glossary: D

Deep Water
Water deep enough so that surface waves are not affected by the bathymetry on the ocean bottom. Generally, water more than 1,000 feet, or at least deeper than one-half the wavelength of the existing waves is considered deep water.

Deepwater Breaks
Surf spots where the swells have a steep transition from deep water to shallow water so the waves are generally bigger and more powerful than elsewhere. Also includes surf spots where the deep water bathymetry of the ocean floor can greatly focus longer period swells (over 16 seconds) to create larger and more powerful waves. Spots with underwater canyons like Blacks are a prime example.

Degrees
A) The unit of measurement for direction to analyze where wind and swell direction is coming from. North is 0 or 360 degrees (12:00 o'clock); and then moving clockwise, east at 90 degrees (3:00 o'clock), south at 180 degrees (6:00 o'clock) and west at 270 degrees (9:00 o'clock). Northeast may be anywhere between 0 and 90 degrees, southeast between 90 and 180 degrees, southwest between 180 and 270 degrees and northwest between 270 and 360 degrees. B) Degrees also are used to measure Latitude and Longitude, with minutes and seconds used a fractionals between the degrees. One degree of Latitude will always equal 60 miles at that same location. One degree of Longitude will always vary due to the curvature of the Earth toward the poles.

Diffraction
The process of wave energy filtering into the lee of obstacles such as breakwaters by the transfer of the wave energy along wave crests. Diffracted waves are smaller than the original waves.

Direction
Where the wind or swell is coming from. In the marine community, directions are always identified as the direction the swell or the wind is "coming from," not the direction it's headed.

Double Up
When two waves combine, often creating an extra powerful wave with twice the amount of energy. Double up waves often create the best waves to get barreled or tubed on because the interaction of the waves forces the waves to break in shallower water than normal, which creates hollower, steeper waves.

Down-the-line
A reference to the direction further along the crest of a wave from the location from where a surfer drops into the wave. The direction toward which the surfer is riding. Waves can also be described as "down-the-line" when the wall is long and fast.

Dumping
Used to describe waves that are very hollow and hard-breaking.

Duration
In wave forecasting, the length of time the wind blows in the same direction over the swell generating area, or the fetch. Duration is one of the three key elements in the fundamental wave generation formula-along with wind velocity and fetch length-used to determine wave heights and wave periods in a storm or wave generating area.