Snorkeling Molasses Reef should be your top priority when in Key Largo. It is the highlight of the area. It is a huge, picture perfect, spur and groove coral reef with a very nice variety of depths.
Because this reef is about six miles offshore, sitting on the edge of the barrier reef, conditions need to be fairly calm to snorkel it. And that is why we have not yet done it. The weather would not cooperate when we were there. But we have heard great things about the wonderful Elkhorn Coral, huge brain corals, abundant sea life, and clear waters.
Because this is one of the further out reefs, you will find bigger species of fish and sea life in general. Expect to see turtles and rays are said to be common here. Goliath Grouper frequent the area. The visibility is also supposed to be excellent because it gets flushed by the ocean currents.
We became pretty familiar with this NOAA weather site when trying to decide if we should snorkel at Molasses. It is a weather station on the 45 foot tower right on Molasses Reef. And it is the best place to check out weather for the Key Largo area.