Cooktown, Australia's closest mainland port to the Great Barrier Reef, sits at the mouth of the Endeavour River with reefs a short boat ride offshore, yet very little recreational diving happens here. There is no dive shop, and local tourism material describes reef trips from Cooktown mainly in terms of fishing, glass-bottom-boat sightseeing and snorkelling, including trips out to the Ribbon Reefs, noting plant corals, gorgonian fans, blue coral and brain coral. Boulder Reef and Egret Reef are reported as reefs visited by Cooktown charter boats, but no published site-level dive descriptions were found for either.

Reefs at this distance, around 20 km offshore, are inner to mid-shelf reefs, which typically have good hard-coral cover, bommies and reef slopes to 15-20 m, with coral trout, emperors, sweetlips, parrotfish, reef sharks, turtles and giant clams. Visibility is best in the dry season and drops in the wet, when the Endeavour and Annan rivers flood. Divers who want to explore these reefs need a charter that will accommodate diving, or a well-equipped private boat, and must bring cylinders from Cairns or Port Douglas.

The combination of remoteness, crocodiles in the river and coastal waters, stingers in the warmer months and long evacuation times means careful planning is essential. For divers already in Cooktown with their own boat, it is a chance to dive reefs that almost nobody else visits. Egret Reef, listed as an alternative name, may be a separate reef nearby; neither name could be matched to a published dive account.

The most practical way for most divers to see the reefs off Cooktown is on a northern liveaboard itinerary from Cairns or Port Douglas that passes the area on the way to Lizard Island and the Ribbon Reefs.

From Cooktown (about 4.5 hours' drive north of Cairns on the Mulligan Highway), launch at the Cooktown boat ramp at the mouth of the Endeavour River or join a local charter; the reefs east of Cooktown are roughly 1-1.5 hours away in fair weather. Cooktown Reef Charters runs fishing, sightseeing and glass-bottom trips on its 42 ft vessel – confirm in advance whether diving is possible. Cross the Endeavour River bar with care.

Bring your own dive gear and cylinders; there is no dive shop in Cooktown.

Cooktown's reefs are exposed to the south-east trade winds, which blow strongly for much of April-September; calm windows are most likely from September to December. Visibility is best in the dry season (May-October) and drops sharply in the wet season when the Endeavour and Annan rivers flood. Box jellyfish and Irukandji are present roughly October-May, and the cyclone season runs November-April.

Currents run hard around reef edges on spring tides. The Endeavour River bar can be dangerous in easterly swell and on a run-out tide.

Anchor in sand in the lee of the reef, dive the reef edge at 5-15 m, turn at a third of your gas and return shallower for a safety stop near the boat.

No regular dive operator – Cooktown Reef Charters (fishing/sightseeing/glass-bottom, enquire about diving) or private boats from Cooktown; northern liveaboards from Cairns and Port Douglas sometimes pass through the area on Lizard Island itineraries; the mooring used on any day is chosen by the skipper according to wind, tide and other boats