USCGC Duane

The Duane earned her keep for five decades - Depression-era patrols, WWII convoy escort, a submarine kill, Vietnam service - before the Coast Guard retired her and Key Largo sank her upright in 1987, one of the first purpose-built dive reefs in the Keys. She sits proud on the sand at 36 m with her mast still climbing toward the surface, and because the Gulf Stream sweeps her regularly, she is the fishiest wreck in the upper Keys: barracuda in ranks along the rails, jacks spiraling the mast, goliath groupers in the deckhouse, and reef sharks appearing when the blue water is on. In clear stream water, hanging on the mooring line above her is the best view in Key Largo.

The moment you come for: An upright, storied cutter in blue Gulf Stream water, barracuda escorts, big grouper

Topography: 100 m Coast Guard cutter upright on sand at about 36 m

Current: The most current-exposed of the Key Largo wrecks - trips get called or converted when the Gulf Stream leans in.

Hazards: Strong current on many days; depth for the full tour; hold the line on ascent and descent.

Conservation: FKNMS artificial reef; moorings mandatory.

Nitrox: Worth it here — profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).