West of Key West, the snorkeling at Dry Tortugas is popular with tourists coming from Key West by ferry and seaplane. The main landing point in the Dry Tortugas archipelago is Garden Key, which is the site of old Fort Jefferson. Most snorkelers only experience the snorkeling dive sites surrounding Garden Key, but there is also some interesting snorkeling off nearby Bird Key and also Loggerhead Key. While originally known for isolated coral head formations, much of the coral growth has been impacted by storms and climate change. Within the expansive sand flats surrounding the islands, there are old coral reefs, rocks and artificial reefs that provide habitat to colonies of typical reef fish. There are plenty of sea fans, sea rods and christmas tree worms along with some small brain corals.
While snorkeling off Garden Key, you'll notice that the water clarity is not particularly good, especially considering how far you've come from the mainland. It doesn't take much wind or wave actions to stir up the sand and sediment in the sand flats to reduce visibility. Typically you can expect the visibility to range from 3 feet to 20 feet. During a Dry Tortugas snorkeling dive, you may encounter butterflyfish, french angelfish, queen angelfish, parrotfish, wrasse, barracuda, sergeant majors, yellowtail, hogfish, grunts, goliath grouper and southern stingrays. In addition, there are several species of turtles including green sea turtles, hawksbill turtles and loggerhead turtles. You may also observe resting nurse sharks and reef sharks.
The Dry Tortugas National Park is located about 70 miles west of Key West. This archipelago is also part of the Florida Keys National Marine Sanctuary. The main island, Garden Key, is the site of old Fort Jefferson and the ferry boat landing pier.
There are four main snorkeling dive sites on Garden Key. Most snorkelers first start at South Beach on the southwest corner of Garden Key. South Beach is mainly a broad grassy sand flat with limited marine life. From South Beach, snorkelers then head out to the far west side of the island to the isolated old coral head formations. These western coral heads are accessible for strong swimmers who will encounter diverse marine life above the coral heads and artifical concrete block reefs. Back at South Beach, snorklers can also head south around to the old southern coaling dock ruins where there is good snorkeling around the old wharf pilings. From shore, you really can't tell how good the snorkeling is around the old pilings. There are plenty of sea rods growing that provides habitat to small reef fish and barracuda. The last snorkeling dive site is located around the corner from North Beach where snorkelers can access the northern coaling dock ruins and its old wharf pilings. Around the northern ruins, keep an eye out for the channel reef sharks which are attracted by all the shore birds landing in the channel waters.
In the past, there are many literature references to good snorkeling in the moat surrounding Fort Jefferson where snorkelers were encountering octopus and yellow stingrays. However, snorkeling is now prohibited in the moat, perhaps due to the resident crocodile now patrolling Garden Key.
While at Dry Tortugas, check in to getting over to Loggerhead Key, which is 3 miles to the east, where there is excellent snorkeling off the old Windjammer wreck. For overnight campers on Garden Key, they are permitted to bring a sea kayak which can be used on very calm days to head over to Loggerhead Key.
Also, just to the southwest of Garden Key, there is some good snorkeling in the waters surrounding Bird Key, which is also accessible by sea kayak.
To reach the snorkeling at Dry Tortugas National Park from Key West, there is a once-a-day ferry that takes 2.25 hours each-way and provides about 4.5 hours at Dry Tortugas. Alternately, there is a twice-a-day seaplane service that takes about 40 minutes and offers about 2.5 hours at Dry Tortugas. Both options are surprisingly expensive, so be prepared. The ferry company does offer a significant discount to local residents with a local ID. Once on the island, keep in mind that there are no services or bathrooms.
To reach the snorkeling in Key West, fly into Key West International Airport (EYW), which is served by several airlines including United/Silver Airways, Delta, USAir and Southwest. Alternately, there is also the regular Key West Express ferry service (4 hours) that runs from Ft Myers.
Overall, Dry Tortugas is the 9th most popular snorkel dive spot of all 40 snorkeling dives in the Florida Keys.