I think Ana posted that without considering the question was for HZ venues. Did some searching and it seems the Q' Fish website is down. There is an article about it here, tho: http://www.latitud21.net/Marzo05/sube.html
El Pescador downtown Cancun. Always forget the street...somewhere around Tulum or so. Best in cancun we have found ever.
That is our favorite seafood restaurant too! Its on Tulipanes just down from the Burger King. We just love the service and the food and prices. The main worker has been there for at least 1993. Once it was raining when we were leaving and he used one of the table umbrellas to escort us to Tulum av for a cab.