Great Detached Reef is one of the headline destinations of the far-northern Great Barrier Reef expeditions. Mike Ball describes 46 km of fringing reef offering multiple sites – Turmoil (hard coral fields to 30 m), Twin Peaks, Oh My Bommie, Cracker and Big Woody – with soft corals, fans, whips and abundant marine life. Spirit of Freedom highlights steep outer walls with gorgonians and soft corals, isolated pinnacles and deep canyons, and notes that much of it remains largely unmapped.

Detached reefs sit on the very edge of the continental shelf, separated from the main reef line. The outer walls drop steeply into deep water, and currents and upwellings sweep along them, bringing nutrients and clear oceanic water. The result is lush soft coral and gorgonian growth, big hard coral fields on the shallower slopes, and abundant fish.

Dive Pacific's account of a Spirit of Freedom trip describes twin pinnacles rising from 60 m to within 4–14 m of the surface, and sightings of whale sharks, silvertip sharks, green turtles, epaulette sharks and barracuda schools. Professional Dive Services lists its own names for sites on the Great Detached and neighbouring reefs, including Captain Blood's Wall of Terror, Da Phat, Turtle Farm, the OMG Spot and Cow Bommie – the naming varies between operators, since few divers ever visit. Great Detached is visited only on expedition liveaboards in the October–December window.

Dives are demanding, with strong currents at times, and operators require Advanced certification or equivalent experience. For experienced divers, it offers the chance to explore reefs that very few people have seen, with pristine coral and the possibility of big pelagic encounters. The individual sites documented in this dataset are listed separately.

Liveaboard only – there are no day boats, resorts or public moorings this far north. Mike Ball Dive Expeditions' Spoilsport runs 7-night 'Northern Exposure' expeditions between Cairns (Trinity Wharf) and Horn Island in the Torres Strait each November (northbound and southbound, up to 27 dives), plus a 7-night Far North Coral Sea Exploratory round trip from Cairns in October. Spirit of Freedom runs 7-night far-north expeditions from Cairns in October–December, and Professional Dive Services' MV Kalinda has run longer (13-night) Cairns–Horn Island trips.

Horn Island has daily scheduled flights to Cairns (book separately; allow 24 hours after diving before flying). The far-northern reefs are roughly 500–650 km north of Cairns – one to two days' steaming each way.

The far-northern reefs are only diveable in a narrow weather window. The south-east trades blow hard from about April to September and make the long open-water passage and the exposed outer walls impractical, so expeditions run in the transition period, typically October–December, when winds are lighter; the northerly monsoon, storms and cyclones (December–April) close the season. Even in the window, exposed shelf-edge walls (Tijou, Great Detached, Raine) need calm days, and skippers switch between reefs to find shelter.

Strong tidal currents and upwellings run along the continental shelf and through reef openings – channel sites are timed to slack water. Visibility varies from about 12 m to 40 m+ depending on tides and any rain. Marine stingers are present from November.

Sites vary (see Turmoil, Big Woody and The Pinnacles); a typical dive drops onto the wall or reef slope at 18–25 m, works along it with the current, then rises onto the reef top or coral gardens for the safety stop and tender pick-up.

Liveaboard only: Mike Ball Dive Expeditions (Spoilsport – 7-night Northern Exposure Cairns↔Horn Island, November; 7-night Far North Coral Sea Exploratory, October); Spirit of Freedom (7-night far-north expeditions, October–December); Professional Dive Services MV Kalinda (occasional long expeditions). Requirements typically Advanced certification or 15+ logged ocean dives.