As surf forecasters we measure waves from the trough (the lowest point) to the peak (the highest point). Typically we do this in feet but of course it’s equally valid in meters. Surfers however indulge in a range of different measuring systems depending on their context which all usually involve underestimating the face height of the waves.
The ‘Hawaiian’ system is intended to measure not the breaking wave face, but the height of the back of the wave as viewed from the water. In doing this the measured height of waves breaking on reef (which tend to pull a deeper trough in front than our ‘idealised’ image of a normal wave) is significantly less than their face height. This system does tend to at least have some consistency with a general agreement on heights.
In our experience most typically surfers describe waist high waves as ’1ft’, waist to chest as ’2ft’, chest to head as ’3-4ft’ and a ’6ft’ wave to most surfers is head and a half or more. The problem with this system is it rapidly degenerates into a chest beating competition to describe the largest waves possible in the smallest terms – this lack of consistency really makes it next to useless for a surf forecast. Check out this photo:
There were surfers describing this day as ‘solid 4ft’ – they’ve every right to call it as they see it but you can start to see that this system isn’t much use for us as surf forecasters. It’s for that reason that on MSW and everywhere we discuss waves we talk in feet, and we talk about the actual trough to peak swell height or the wave face height. Given this the scale looks something like:
1ft – Ankle to Knee High
2ft – Knee to Thigh
3ft – Waist Hight
4ft – Chest High
5ft – Head High (for average rider slightly crouched down)