The Brook Islands are a small group of national-park islands north of Hinchinbrook Island, visible from the Bruce Highway near Cardwell. Queensland Parks says the western sides of the islands are popular for swimming and snorkelling, and marinelife.org.au describes coral formations here as among the oldest and largest single formations yet found on the Great Barrier Reef, a remarkable claim for an inshore reef and one that makes the islands worth a visit for keen reef watchers. The islands are best known for birds: more than 40,000 pied imperial-pigeons breed here in summer, returning to their nests each evening in great flocks, along with several tern species and the vulnerable beach stone-curlew.

To protect them, landing on the islands is prohibited, and the surrounding water is a Marine National Park Zone where fishing and collecting are banned. Boating is managed under the Hinchinbrook Plan of Management, with speed limits, a 35 ft vessel limit, no-anchoring areas and public moorings. Underwater, the fringing reefs are shallow and turbid by outer-reef standards, with visibility often 3-10 m, but the coral cover is significant, including very large massive coral colonies, and turtles and reef fish are common.

There is no dive operator, so visits are by private or charter boat, and divers must be self-sufficient. Estuarine crocodiles live in the Hinchinbrook Channel and surrounding waters, and stingers are present in the warmer months. It suits snorkellers and shallow divers with their own boat who value quiet reef and birdlife.

Visiting in the late afternoon in summer allows boaters to watch the pigeons return from the mainland rainforest.

The Brook Islands lie roughly 15-20 km east-north-east of Cardwell on the Bruce Highway (about 2 hours 45 minutes south of Cairns) and about 30 km south of Mission Beach. There is no regular dive operator: go by private or charter boat from the Cardwell boat ramp or Port Hinchinbrook marina, or from Mission Beach. Public moorings are available first-come, first-served; vessels over 35 feet are not allowed, speed is limited to 6 knots within 200 m of the islands, and anchoring is banned in marked no-anchoring areas.

Landing on the islands is prohibited.

The Mission Beach reefs are exposed to the south-east trade winds, which blow 15-25 knots for much of April-September and can cancel trips; the calmest months are usually September-December. Box jellyfish and Irukandji are present from about October-November to May, most dangerously close to the coast, so wear a full stinger suit. The cyclone season runs November-April, and Mission Beach has been hit hard by cyclones Larry (2006) and Yasi (2011).

Heavy wet-season rain and river flood plumes from the Tully and Johnstone rivers reduce visibility on the inner reefs. The western sides of the islands, favoured for snorkelling, are sheltered in south-easterlies. Visibility is often low because of runoff from the Herbert, Tully and mainland creeks, especially in the wet season.

Pick up a public mooring on the western side, snorkel or dive the reef edge at 2-8 m, looking for the large coral formations, and return to the boat. Do not land on the islands.

No regular dive operator – private boats and occasional charters from Cardwell, Port Hinchinbrook or Mission Beach; Cardwell-based fishing and eco-tour charters can drop snorkellers on a mooring by arrangement; the mooring used on any day is chosen by the skipper according to wind, tide and other boats