I can email you the full text Giles if you want me to.
It is quite interesting.
They did break the photographers in to two groups, non specialists with disposable and specialists with expensive cameras. They fond no difference in the two groups.
The study consisted on 26 weeks of observations. In 2 13 week periods, one during the winter=high tourist season, and one during the summer=slow season.
The biggest complaint I have about the study is their definition of "diving impacts" this includes any contact with the substrate, be it sand, dead rock, or live coral. Also, you dont even have to touch the substrate to be classifyed as an 'impact'. Any action that causes sediment to be released into the water is classifyed as 'impact'
They blame shore divers as being considerbly worse on the reef than boat divers, after all you have to walk through that sand in order to get out. They found that 97.9% of shore divers contacted the reef. I question how the other 2% got in the water without touching the sand. Pier maby??
Divers holding onto the substrate with their hands and resting against the substrate with their knees were the next most problematic actions
I am suprised that they dont note open water classes as the epitome of evil, after all 50% of the time is spent resting on your knees on the substrate=sand.
Then they finish off the study saying it is unknown if direct physical contact with live coral causes damage. They refrence a study that found there is no damage done to a coral by touching it. Yet they also explain that touching the sand is bad because you stir it up and later a sand partical may land on a coral. OHH NO
Of the impacts that actually caused damage to the reef = 'breakage' they found that photographers are to blame, after all there is a week correlation.
Photographer status was the only significant predictor of breakage rate among the independent variables for boat and shore dives, although the regression was weak......Coral breaks by divers were few, but it appears that when they did occur, being a photographer had some, albeit small, influence. Predicted number of breaks min−1 for any one dive for photographers was 0.032 and for non-photographers 0.006.
So photographers may be likely to sit in the sand or push off of a dead piece of rock but when it comes down to doing anything that definately causes damage to the reef, it is so rare, that the difference could pretty much be explained by a single photographer who kicked a piece of A. cervicornis and broke a dosen tips off.
It looks like to me that divers cause so little direct damage to the reef it would have taken them years to gather enough data to produce any strong results if they just counted direct damage.