I know that island sewage is often not well treated. Are you sure the cruise ships are just dumping it overboard?Ive been seeing an increase in the algae starting around the end of Bricks area for the past several years. Each time I start back diving after my summer whale shark sabbatical, my eyes are always seeing more and more growth. Its all related to the sewage and discharge from the island. Its all limestone and most of the sewage is just dumped through into the ground and it leaches out into the ocean. All the new beach clubs, new condo developments are making matters much worse. The Kuza beach club buried protected mangroves so they would have more land to use....no penalties there eventhough its a federal crime. Look at Columbia shallows....it's pretty much dead now. The cruise ships bring in probably 40000 people every day during high season....that's a lot of toilets being flushed and it ain't going into a treatment plant....Royal Carribean bought Playa Mia beach club and is doing a massive build there. Where is all their untreated pool water going to go? All their sewage.....