You can use them as just a source (air/rentals).... even packages with rental vehicles
But, also you can just relax...
With them it is "concierge" shore diving (I didn't say botique, you help out with carrying/loading stuff.). Worry free. My gear is with them while I am there, drying in the air, and secured overnight, out again for me in the morning. Rinse tanks and showers, bathrooms and beverages on my return. They know the Island (hassles of driving), and they know the spots (nice to have local knowledge of the small critters, but also they are not hearding you). Choice parking. Food, snacks, and beverages with each trip all on the ready. Fun to be around (it is a social experience too). I don't have to even think about things like gas stations. No worries about trashing a rental car (sand/water/road damage).
Lots of positives....