If "Blue Hole" has fresh water in it, why don't they just lay a pipeline to it? Or is it protected coral reef? Like Tarpon Springs in Florida the coral formed limestone is obviously filtering the sea water by taking the salts out of it.
Carlsbad Caverns is another classic example of that. The water in the cave is real sweet good water. But the surface water is bad alkali water,full of mineral salts like sea water.
Seems like CWCO could do a small siesmic survey to map the cave the water comes out of at Blue Hole? Then tap it the cave with a shallow water well? Any well under 2500 ft is considered shallow.