I just got back from Coz a few weeks ago (scroll down to read a long, opinionated trip report). We stayed at the Presidente. I can highly recommend it. I haven't stayed anywhere else in Coz, so I can't comment on other hotels. Snorkling is easy due to piers over the ironshore and ladders straight down into the water. Lots to see snorkling. Sandy beach is small and manmade, but quite nice and well kept. Tennis courts on site. Golf nearby. Fancy eatery was undergoing rehab while we were there, but the open-air cafe was quite good. Nice pool, though that is, as usual, where the kiddies hang out. We had a ground floor garden view room and loved it. Many ocean view and ocean front rooms are available, however. $5 cab ride each way to town. No fridge or safe in the room. Ice is made with purified water, but don't drink the tap water. Hotel only supplies 1 gratis liter of bottled water each day, so plan to buy more. It's expensive at the hotel. We bought water and bodacious quantities of cerveza at the "mini super" stores in town for cheap. Cheap water and soda is available also in the many farmacias in town. We took a large soft sided cooler to store our comestibles in.
Everyone says the Presidente is expensive, and it is. But it isn't as expensive as many comparable resorts we've visited in other dive destinations. Grand Cayman and Bermuda come to mind as being more expensive for similar quality resorts.
