Top Sites: Devil's Throat (deep/advanced dive), Palancar Reef, Chankanaab Caves (must have good vis for a good dive here), C52 Wreck, Paradise reef.
Water Temp/Gear to Take: mid 80Fs so take 3mm, skins or rash guards. Amazing vis in Cozumel. Can be rather hot in the summer - take lots of sunscreen.
Places to Go: Chankanaab park for the beach and cave dives, El Cedra and NE region for the temples/ruins, SE beachs are long and relaxing, street taco vendors in the City Centre