Just over 4 and a half days. I think no wait maybe actually yes no I'm not sure really.

Hawaiians started the back of wave measuring for surf height and it has been adopted through much of the surfing fraternity as they are such a humble crew that they don't want to run the risk of over exaduration and the associated ridicule.

But there are a few other things to consider swell height etc... As
reported by weather reports or marine forecasts are not surf height

surf reports are a general guide only as they can only be accurate if they are break specific as different breaks will always have different wave heights. Due to the nature of the bottom formation.
So you could be surfing a shallow hollow reef break where the bottom depth goes from deep to super shallow in a very very short distance and a mate could be surfing a totally different break just a few 100 m away that is fat and slow and you will have totally different experiences. So later that day in the pub one says he was out in Overhead pits and the other says it was 4ft and mellow ... Yet they were in the same area..... And so the argueing starts.

When Hawaiians argue people get messed up ...so maybe they decided .. To avoid confusion we will measure the back of the wave.

Teahupoo is a perfect example of the difference the bottom contour makes to the wave face height. You will notice that the pit in front of the wave is actually sucking up from below sea level. The wave from the back looks just like any other rather large wave only when you view it from the front does it become the beast it is. There are other waves in the area that with the same size swell on the same day facing pretty much the same direction that whilst still large are not the bus eating monsters that the chopes reef is making.

IPhone + Forum + lamb korma = dunny and a long post......... Sorry