Gloucester Passage is the narrow channel separating Cape Gloucester on the mainland from Gloucester Island, a steep, forested national park island east of Bowen and north of the Whitsunday group. The passage is a popular anchorage and fishing area, and on its fringes – along the Gloucester Island shoreline and its western bays – fringing reefs offer snorkelling and diving for those with a boat. Published dive documentation is sparse.

The sailing guides describe channel depths of 3–6 m at low water with deeper water in the centre, anchorages over sand at Montes Reef Resort (5–10 m), Cape Gloucester Resort (4–8 m), Bona Bay on Gloucester Island (6–12 m) and Middle Bay (7–12 m), and tidal flows commonly reaching 2–3 knots on springs. Divers should expect granite boulder shorelines grading into fringing reef of hard corals, with sand and rubble below. Fish life around such current-swept island reefs is usually good: sweetlips, trout, trevally and reef fish, turtles and occasional rays.

The current is the defining challenge. Diving should be restricted to slack water on neap tides, and to the sheltered bays rather than the channel itself. Wind against tide creates short, steep chop that makes pick-ups difficult.

The area has good support ashore: Dingo Beach has a boat ramp, and Hydeaway Bay, Cape Gloucester and Montes Reef resorts offer accommodation and food. For Bowen-based divers with their own boat, Gloucester Island is the nearest island diving and a gateway to Holbourne Island further offshore.

Drive from Bowen about 45–60 minutes south-east via the Bruce Highway and Gregory–Cannon Valley road turn-off to Dingo Beach, Hydeaway Bay or Cape Gloucester (Montes Reef Resort and Cape Gloucester Resort at the passage). Launch at the Dingo Beach boat ramp (or from Bowen harbour, about 1 hour by boat) and run to the passage. Anchor on sand: Bona Bay on the western side of Gloucester Island (6–12 m) gives good protection in south-easterlies; off Montes Reef Resort (5–10 m) is sheltered in the trades but exposed to northerlies.

Channel depths are only 3–6 m at low water.

Tidal flow is the dominant factor: currents through Gloucester Passage commonly reach 2–3 knots on spring tides, and wind against tide throws up a short, confused chop, especially near the northern entrance. Dive only at slack water, ideally on neaps. The bays on the western side of Gloucester Island are sheltered from south-easterlies; Montes Reef and Cape Gloucester anchorages are exposed in northerlies.

Visibility of 3–10 m is typical, worse after strong winds and wet-season rain. Marine stinger season (box jellyfish and Irukandji) runs roughly November to May – wear a full-length stinger suit or wetsuit with hood and gloves, carry vinegar. Cyclone season November–April; tropical lows and cyclones can close sites and damage coral (TC Yasi 2011, TC Debbie 2017).

Anchor in Bona Bay or another sheltered bay on Gloucester Island and dive the fringing reef at 3–10 m at slack water, staying close to the reef and out of the main channel. If drifting the passage margins, use an SMB with a boat following.

No regular dive operator; private boats from Dingo Beach and Bowen, NQUEC club trips, occasional charters. Nearest dive centres for gear hire, fills and local advice: Whitsunday Dive Adventures (Airlie Beach), Adrenalin Snorkel & Dive (Townsville).