Editing Surfing (section)

===Tube shape and speed===
[[File:Wave-shape-intensity.svg|thumb|upright=1.35|The [[geometry]] of tube shape can be represented as a ratio between length and width.]]

Tube shape is defined by length to width ratio. A perfectly cylindrical [[vortex]] has a ratio of 1:1. Other forms include:
* Square: <1:1
* Round: 1–2:1
* Almond: >2:1

''Peel'' or ''peeling off'' as a descriptive term for the quality of a break has been defined as "a fast, clean, evenly falling curl line, perfect for surfing, and usually found at pointbreaks."<ref>{{Cite book|last=Warshaw|first=Matthew|title=The Encyclopedia of Surfing|publisher=Harvest Book Harcourt Inc|year=2005|isbn=978-0151--00579-6|location=Orlando|pages=e.g. 452}}</ref>

Tube speed is the rate of advance of the break along the length of the wave, and is the speed at which the surfer must move along the wave to keep up with the advance of the tube.<ref name="Lewis et al 2015" /> 
Tube speed can be described using the peel angle and wave celerity. Peel angle is the angle between the wave front and the horizontal projection of the point of break over time, which in a regular break is most easily represented by the line of white water left after the break. A break that closes out, or breaks all at once along its length, leaves white water parallel to the wave front, and has a peel angle of 0°. This is unsurfable as it would require infinite speed to progress along the face fast enough to keep up with the break. A break which advances along the wave face more slowly will leave a line of new white water at an angle to the line of the wave face.<ref name="Lewis et al 2015" /><ref name="Mendonca et al 2012" />

:<math>V_s = \frac {c}{sin \alpha}</math><ref name="Lewis et al 2015" />

Where:
:<math>V_s = </math>velocity of surfer along the wave face
:<math>c = </math>wave celerity (velocity in direction of propagation)
:<math>\alpha =</math>peel angle

In most cases a peel angle less than 25° is too fast to surf.<ref name="Lewis et al 2015" />

* Fast: 30°
* Medium: 45°
* Slow: 60°

{| class="wikitable" style="text-align:center"
|+Wave intensity table
|-
! !! Fast !! Medium !! Slow
|-
! Square
| [[G-Land|The Cobra]] || [[Teahupoo]] || [[Shark Island, Cronulla Beach|Shark Island]]
|-
! Round
| [[G-Land|Speedies]], [[Gnaraloo]] || [[Banzai Pipeline]] ||
|-
! Almond
| [[Lagundri Bay]], [[Snapper Rocks|Superbank]] || [[Jeffreys Bay]], [[Bells Beach, Victoria|Bells Beach]] || [[Angourie Point]]
|}