You have a problem with a dive boat.
The two conditions it runs in are very different so props will always be a compromise.
If you prop it for loaded condition you get the best performance most of the time but because it is a club boat you always get some yahoo who will over rev it when empty (and it is empty quite a lot when divers are in the water) Some folk either don't know or care what they are doing with it as it doesn't belong to them.
If you prop it for empty you lose performance when its full (again, a lot of the time).
It depends on whether you think it will be abused which option you choose. I would probably prop it for full and put a bit sticker or similiar saying max revs on the rev counter with a boat rule threatening dire consequences to folk that ignore it