The Florida Keys string roughly 180 km of islands from Key Largo to Key West inside Florida Keys National Marine Sanctuary — the most-dived destination in the United States, pairing the continental US's only coral barrier reef with two of the world's largest artificial-reef wrecks, the 155 m Spiegel Grove and the roughly 160 m Vandenberg.
Destination info
Conditions, highlights, and the resident marine life.
Conditions
Water and air temperature across the year.
WaterAirDryShoulderWet
Description
Florida Keys National Marine Sanctuary, designated in 1990 and expanded to 4,539 square miles under the January 2025 Restoration Blueprint final rule, protects more than 6,000 animal species, the only coral barrier reef in the continental United States, and the largest documented contiguous seagrass community in the Northern Hemisphere. Diving is year-round and overwhelmingly day-boat: shallow spur-and-groove reefs at 2–12 m (Molasses, Sombrero, Looe Key), the Christ of the Abyss statue at Key Largo Dry Rocks, a sanctuary Shipwreck Trail of historic wrecks like the 1942 Benwood, and two purpose-sunk giants — the 155 m Spiegel Grove (2002, Key Largo) and the roughly 160 m USNS Vandenberg (2009, Key West). The Gulf Stream keeps water warm (low 20s °C in winter to about 31°C in summer) and often clear, but the reefs are honestly diminished: roughly 90% of live coral cover has been lost over 40 years, stony coral tissue loss disease has burned through the tract since 2014 (still present, though no longer at epidemic proportions per the sanctuary), and the record July 2023 marine heatwave caused mass bleaching and near-total mortality of staghorn and elkhorn restoration stock. NOAA's Mission: Iconic Reefs program is rebuilding seven signature reefs toward self-sustaining levels by 2040, and the Restoration Blueprint's updated zone rules have applied in federal waters since March 2025 while Florida's governor vetoed their application in state waters. Hurricane season runs June through November; winter cold fronts bring wind and reduced visibility.
Highlights
What makes this dive worth the trip.
Florida Keys National Marine Sanctuary protects more than 6,000 animal species, the only coral barrier reef in the continental United States, and the largest documented contiguous seagrass community in the Northern Hemisphere — making it one of the most heavily dived marine protected areas in the world.
The 155 m (510 ft) ex-USS Spiegel Grove was the largest ship ever intentionally sunk as an artificial reef when scuttled off Key Largo in 2002; REEF's five-year monitoring project documented 191 fish species on the wreck, with 46 species recorded less than a month after deployment.
The roughly 160 m (524 ft) USNS General Hoyt S. Vandenberg, a Cold War missile-range tracking ship, became the second-largest artificial reef in the world when she was sunk seven miles south of Key West on May 27, 2009, settling upright in about 45 m of water.
Marine life
33 species you’re likely to encounter on a dive here.
Dive sites
7 signature sites at this destination.
Spiegel Grove
A 155 m (510 ft) Thomaston-class landing ship dock scuttled six miles off Key Largo in May 2002 — at the time the largest vessel ever intentionally sunk as an artificial reef. She sank prematurely and rolled onto her starboard side; Hurricane Dennis pushed her fully upright onto her keel in July 2005. The superstructure starts around 18 m and the hull sits in roughly 40 m on the sand, with so much ship that operators say you could dive her dozens of times without seeing it all. Goliath grouper, big barracuda, and dense schools of jacks patrol the decks; penetration is for wreck-trained divers only.
18–40 madvancedDay boatModerateVisibility 12–30 m
USNS General Hoyt S. Vandenberg
A roughly 160 m (524 ft) former troop transport and Cold War missile-range tracking ship sunk seven miles south of Key West on May 27, 2009, becoming the second-largest artificial reef in the world at the time. She rests fully upright in about 45 m of water; the famous radar dishes and superstructure rise to within 12–21 m of the surface and the main deck lies near 30 m, so divers of different levels can work different tiers of the ship. Thousands of fish swarm the structure, with goliath grouper and barracuda as reliable residents.
12–44 madvancedDay boatModerateVisibility 15–30 m
Christ of the Abyss (Key Largo Dry Rocks)
A 2.7 m bronze statue of Christ by Guido Galletti — the third cast of the famous San Fruttuoso original — placed in roughly 8 m of water at Key Largo Dry Rocks on August 25, 1965. Now inside Florida Keys National Marine Sanctuary just outside John Pennekamp Coral Reef State Park, it is one of the most photographed underwater sites on Earth and is shared by snorkelers and divers on the same shallow reef, which is dotted with brain and star coral heads.
2–8 mbeginnerDay boatLightVisibility 10–25 m
Molasses Reef
A 247-acre Sanctuary Preservation Area six miles off Key Largo with a classic, well-defined spur-and-groove system, numerous boulder corals, and famously clear water — NOAA calls it the most heavily visited reef in the Upper Keys and perhaps the most visited reef dive in the world. Over 30 mooring buoys serve named features like Winch Hole, the Aquarium, Hole in the Wall, and Eagle Ray Alley, with depths from about 2 m on the reef crest to 27 m on the deeper buoys. A no-take zone, so fish life is dense and approachable.
2–27 mbeginnerDay boatLightVisibility 12–30 m
Sombrero Reef
The signature reef of the Middle Keys, four miles off Marathon, marked by the 43 m (142 ft) cast-iron Sombrero Key lighthouse completed in 1858. A Sanctuary Preservation Area with classic coral spurs separated by sandy grooves running from just below the surface to about 9 m, it is one of NOAA's seven Mission: Iconic Reefs restoration sites — its restoration nurseries suffered total losses in the 2023 marine heatwave and replanting is ongoing. Easy conditions and dense schooling fish make it the standard Marathon reef trip for divers and snorkelers alike.
1–9 mbeginnerDay boatLightVisibility 10–30 m
Looe Key
A spur-and-groove reef six miles off Big Pine Key in the Lower Keys, named for HMS Looe, which wrecked here in 1744. Long coral fingers separated by white-sand channels run from about 2 m to 10 m, home to more than 150 fish species including resident goliath grouper, passing reef sharks, and trios of spotted eagle rays; the fore reef drops steeply toward 30 m where the current picks up for drift dives. A Sanctuary Preservation Area and another of the seven Mission: Iconic Reefs restoration sites.
2–10 mbeginnerDay boatLightVisibility 10–30 m
Benwood
A 110 m (360 ft) Norwegian-flagged merchant freighter that sank on the night of April 9, 1942 after colliding with the tanker Robert C. Tuttle — both ships running blacked-out against German U-boats. The wreck lies broken between French Reef and Dixie Shoals in 8–14 m of water, later flattened by salvage and target practice, and is now one of the most popular wrecks on the sanctuary's Shipwreck Trail. Its shallow, current-free profile makes it the Upper Keys' classic second dive and a favourite night dive, with encrusted hull plates sheltering grunts, morays, and lobster.
8–14 mbeginnerDay boatLightVisibility 10–25 m
Where to dive & stay
Local dive centers, resorts, and hotels.
Featured operators coming soon
Verified dive centers, resorts, and hotels around Florida Keys will list here — pricing, photos, and direct contact.
