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Overview
Six miles southeast of Key Largo inside the Florida Keys National Marine Sanctuary, French Reef is the cave network of the upper Keys. Three large caverns named Christmas Tree Cave, Sand Bottom Cave, and Hourglass Cave cut through the spur and groove formations between 5 and 12 metres, packed with shimmering schools of glassy sweepers and the occasional resident green moray. The shallow reef carries elkhorn and brain coral, Christmas tree worms erupt from the coral heads, and southern stingrays, nurse sharks, and eagle rays patrol the sand channels. French Deep on the southeast corner drops past 25 metres into deeper water for a wall style finish.
Briefing note
Sanctuary Preservation Area. Anchoring, spearfishing, lobstering, and coral contact are prohibited; tie to one of the 17 yellow mooring buoys. Reef safe sunscreen required. Several caverns are true swim throughs with sand floors but they can silt out quickly, so a light and good buoyancy help.
What you'll see
12 species curated- year-roundGlassy sweeper
- year-roundGreen moray
- year-roundChristmas tree worm
- year-roundElkhorn coral
- year-roundSouthern stingray
- year-roundNurse shark
- seasonalSpotted eagle rayPeak: Mar · Apr · May · Jun · Jul · Aug · Sep · Oct
- rareGoliath grouper
- year-roundHogfish
- year-roundStoplight parrotfish
- year-roundSergeant major
- year-roundGreat barracuda
Reef data for this area
Jurisdiction-level snapshotsBenthic snapshot — NOAA NCRMP
Florida Keys (NCRMP)
Current mean coral cover
6.7%in 2022
Earlier survey
6.2%in 2014
↑ +0.5 pts
Stratified random benthic transects across NCRMP Florida domain (fore-reef + patch reef sites). Florida Reef Tract has been at historically low cover since the late-1990s white-band epidemic; SCTLD spread (2014–present) and the 2023 marine heatwave have kept means in single digits.
Reported at the jurisdictionscale, not the dive site — the published surveys don’t resolve a single reef. NOAA NCRMP Florida benthic 2022 status report →
Conditions
| Month | Water | Visibility | Current |
|---|---|---|---|
| Jan | 22–24 °C | 12–22 m | mild |
| Feb | 22–24 °C | 12–22 m | mild |
| Mar | 23–25 °C | 15–25 m | mild |
| Apr | 24–26 °C | 18–28 m | mild |
| May | 25–28 °C | 20–30 m | mild |
| Jun | 27–29 °C | 20–30 m | mild |
| Jul | 28–30 °C | 22–30 m | mild |
| Aug | 28–30 °C | 22–30 m | mild |
| Sep | 28–30 °C | 18–28 m | mild |
| Oct | 26–28 °C | 15–25 m | mild |
| Nov | 24–26 °C | 12–22 m | mild |
| Dec | 22–24 °C | 12–22 m | mild |
Season calendar
Peak season highlighted · current month outlined
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