Montgomery Reef is described as the world's largest inshore reef, about 400 km² and 80 km long. With tides of up to 10 m, more than 4 m of reef is exposed at low water, and as the tide falls, water pours off the reef platform in torrents, forming a river through the reef and hundreds of cascading waterfalls. Turtles, manta rays, blacktip reef sharks, dugong and wading birds gather to feed in the outflow.

It is one of the signature sights of Kimberley cruises and appears in local boaters' lists of potential dive spots, and the WA Museum sampled intertidal habitats here. In practice, the tidal torrents, turbidity and crocodile and shark risk mean it is viewed from boats rather than dived; any in-water activity should only be at slack water with expert local guidance.

Kimberley diving context: the Kimberley coast between Broome and Wyndham is one of the least-dived coastlines in Australia. Huge tides (up to 10–11 m), turbid inshore water, saltwater crocodiles around the islands and rivers, and large sharks mean that inshore diving is generally discouraged by experienced local boaters, and expedition cruise ships mostly offer snorkelling or Zodiac excursions rather than scuba. The serious diving is offshore, on atolls and island reefs far from river run-off, visited on a handful of liveaboard departures a year from Broome or Darwin. Medical help is many hours away; divers should be conservative and carry DAN or equivalent evacuation cover.

Planning notes: this is primarily a snorkelling site. Expect to spend most of the dive around 3 m, with a maximum of about 10 m. It can only be reached on a multi-day expedition or liveaboard, so it is usually one of several sites dived on the trip and choices are made by the crew on the day. Currents are significant, so timing around the tide is part of the plan. Best season: September–November (calmest window). Traffic: remote/expedition only.

Visited on Kimberley expedition cruises (Broome–Wyndham/Darwin), usually by tender at falling tide to watch the reef drain, and by private vessels. About 20 km offshore in the Kimberley's Camden Sound region, roughly 130 km south-west of Bardi. Access is within Dambimangari sea country; cruise operators hold arrangements with Traditional Owners.

Expedition vessels typically depart Broome or Darwin (or Wyndham) on 10–14 night Kimberley voyages, or on dedicated 7–12 night reef expeditions; private vessels need full offshore capability, long-range communications (satphone/EPIRB) and fuel for several hundred nautical miles. Dives are run from tenders launched from the mothership, which anchors in the lee of the reef.

Kimberley offshore trips run in the dry season (roughly April–October; Scott Reef and Rowley trips cluster September–November when winds ease). The wet season (November–April) brings cyclones, and the Kimberley coast has tides up to 10–11 m, creating violent currents, whirlpools and tidal races near the mainland and inshore reefs. Offshore atolls have smaller ranges but strong currents in channels.

Strong easterly trade winds in mid-dry season can make crossings rough.

Not recommended for diving: view from a tender as the reef drains on the falling tide.

Kimberley expedition cruise operators visit daily in season by tender (viewing, not diving). No dive operator; diving not recommended.