Responses from divers will likely be along a similar theme.
I have seen island development and causational reef degradation from a very different perspective.
Every time you touch the dirt, you disturb root structures and create run-off sedimentation. That is what kills reefs, not diver visits. Good luck on trying to build our perception of an "attractive romantic" guest room without causing environmental havoc.
If you allow dive-dock showers over the ocean, do not allow soap- just fresh water rinse-offs.
The biggest thing: have the guts to tell your DM's that they must put their tips at risk by being unfailingly proactive when dealing with dragging SPG's, glove use, muck-stick pokers, and the "I only finger-touch dead stuff" Photographers.
When you have caused enough interest in the local area that you incite competitors to set up shop next door, it's all over at that point.
I am in about 90% agreement with DeputyDan's posts above, as I understand that resorts in the SoPac (inferring this by your profile location) sometimes cater to North Americans who want a minimum choice of being able to actually do all 4 dives offered in a day, versus Euro-Asian divers who are used-to only being able to select two (or three) from the four that are offered. North Americans will likely clamor for a night dive, as well.
Again, as in the CoCoView example, this points up another perceptional fallacy found in what divers say versus what they really do. Many people who come to CCV were put-off by the lack of diving availability on arrival day- so they changed that process. Suffice to say, if you do five a day, you'll get that 27 in a week. Do many divers do this? No, and in fact, most do substantially less- yet the clamor continues for being allowed to dive on day one. Less-so in this example, but a lot of dive-resorts have guests who spend a whole lot of the time with an alcoholic beverage in their hand.
Recycling (again in the example for CCV and Honduras) can be a difficult concept for visitors to get their heads around. We in the US are led to believe that recycling actually works as an economically sustainable thing. It kind-of comes close in the US, but is perverted by laws and subsidies. Recycling in your environment will likely be problematic. Best to avoid such items. Ask customers to take-home used batteries and cxyalume sticks... crap like that.
DeputyDan refers above to CoCoView which was built with a very forward thinking approach to being eco-friendly, even though it was built 30 years ago. Efforts such as expending great amounts of money to build a waste-water facility some 10 years ago was way ahead of it's time, but the volumes of money and time spent on establishing a turtle rehab facility simply didn't work out. The common element always shines through in these efforts, that is what your customers will recognize, remember and value as to your reputation.
Every visitor saw and appreciated the ill-fated turtle program, but no one notices the very successful on-site waste-water treatment facility. Makes you think, eh?