South of Marathon Key, the snorkeling on Delta Shoals offers good spur and groove coral formations in 10 to 25 foot deep water spread over a half mile. The brain coral and star coral provides good habitat for lobsters and crab. There are also numerous wrecks in the area.
An interesting area for Delta Shoals snorkeling is the landward side to the north where the Delta Shoal Barge (aka Flaglers Barge) wreck can be found. It is known for its dense marine life, nurse sharks and southern stingrays.
The Delta Shoals snorkeling area is located 1 mile east of the Sombrero light. It is unmarked and has no mooring buoys.
Tip - After a long day of snorkeling at Delta Shoals, then grab some grub conch at Morada Bay Beach Cafe in Islamorada or Saltys Waterfront Grill for some cold drinks. And, if you didn't happen to spot any turtles while snorkeling off Marathon Key, you can always stop by the Turtle Hospital for a top of the hour tour of the hospital or turtles tanks located at mile post 48.5.
While the snorkeling at Delta Shoals is possible year-round, most snorkelers usually shoot for March through September. There is usually some rolling surf at most snorkeling sites off Islamorada, while you can expect the flatest surf conditions from June through August.
When using a dive boat charter to reach the dive site, make sure to reconfirm the reservation the afternoon prior. Most dive boats select the site the afternoon prior or even the morning of the dive. Also, most dive boats have a minimum passenger requirement in order to leave dock meaning they may cancel at the last minute, so when reverifying the afternoon prior ask how many reservations they have. To reach the snorkeling in the Florida Keys by air, there are several options. The most popular option is to fly into Miami International Airport (MIA), which is served by all major US and international airlines. Also nearby, a potentially lower cost option is to fly into Ft Lauderdale airport (FLL). From either of these airports, you can rent a car to drive south on the Florida Turnpike a couple hours to reach the Florida Keys (watch out for automated cash-less toll highways along the way). Alternately, you can fly into Key West International Airport (EYW) which is served by several airlines including United/Silver Airways, Delta, USAir and Southwest. If you don’t mind coming into Key West, there is also the regular Key West Express ferry service (4 hours) that runs from Ft Myers.
Overall, Delta Shoals is the 24th most popular snorkel dive spot of all 40 snorkeling dives in the Florida Keys.