If you are looking for a dive operation in Key Largo -- look no further than Quiescence. This outfit is top shelf! I've dived all over the Caribbean and some South Pacific places, and can honestly say this outfit is the cream of the crop. Why? Because every staff person I met was sincerely friendly, extremely helpful, demonstrated a 'can do' attitude, and all the while giving the impression they really liked their work and valued me as a customer. Their boats are clean, orderly and well maintained. True, they don't put a dive professional in the water with you, but that option is available if you want to hire one. The dive briefings were informative and detailed. If you listen, you will know how to dive and enjoy each site even without a guide. Their service is top notch. My friend's reg had a free flow problem. They loaned him a reg so he could dive, and repaired his while we were diving. They explained what was wrong with his reg and what they did to fix it. And get this -- they charged him only for parts, no labor, and the loaner reg was also no charge. As I said, look no further than Quiescence. And on top of all this, they have a maximum of 6 divers per boat. Tough to beat. 
