Hole in the Wall is named for a large opening through the reef, wide enough for two divers side by side, at about 20 m. Around it, the reef is full of crevices, ledges, drop-offs, tunnels and channels, and the dive continues out to a formation the guides call Paradise Bommie. The site often experiences strong currents, which is precisely why it is so productive: the moving water attracts manta and eagle rays, and large Spanish mackerel hunt along the reef edge.

Reef sharks, stingrays, turtles and moray eels are common, and the walls carry soft corals and sea fans with greasy cod, angelfish, lionfish and Moorish idols among them. Rare nudibranch species have been recorded here, so macro fans should look closely at the walls in sheltered spots. Because of the current, the dive is typically run as a drift once divers leave the hole and bommie, and divers should be comfortable with moving water and staying with their buddy and guide.

The hole itself is short and open at both ends, but it should still be treated with care: avoid kicking up sand or touching the walls. Hole in the Wall suits divers with some experience, ideally Advanced certification, who want a more dynamic dive with a good chance of pelagic encounters. It is one of the more exciting sites on Heron Reef when conditions line up.

When the current is too strong for the full route, guides may shorten the dive to the hole and the sheltered side of the reef, so be prepared for the plan to change on the day and listen closely to the briefing.

Heron Island is 72 km north-east of Gladstone. Fly or drive to Gladstone, then take the Heron Islander ferry from the Gladstone Marina terminal (72 Bryan Jordan Drive; check-in from 7:45 am, departs 9:30 am on scheduled days, about 2 hours), or transfer by seaplane or helicopter. Dive gear is carried on the ferry in addition to baggage.

On the island, the dive centre sits beside the harbour; boats leave the jetty for three dives daily and most Heron Reef sites are 5-15 minutes away. Hole in the Wall is a short boat ride (5-10 minutes) from the jetty.

Heron Reef sites are chosen on the day by wind and tide. The prevailing south-east trade winds (strongest April-September, often 15-25 knots) make the southern and south-eastern reef edge rough, so the sheltered northern and western sites are dived most. Northerly winds in spring and summer reverse this.

The tidal range is up to 3-4 m and currents run strongly around the reef edge and through Wistari Channel on springs; visibility is usually best on the incoming tide. Cyclone season is November-April; summer storms and plankton blooms can drop visibility to 10 m. Stingers are uncommon this far south but present in summer.

Currents are often strong at this site; it is run as a drift or timed for a slower phase of the tide.

Descend and pass through the hole in the reef (two abreast) at around 20 m, then swim or drift out to Paradise Bommie, staying close to the reef to shelter from the current. Circle the bommie watching for mantas and eagle rays, then drift along the reef, ascending gradually to the safety stop.

Heron Island Resort Dive Centre is the only operator: three guided boat dives a day (about 9 am, 11 am and 3 pm) plus scheduled night dives, from the resort jetty; sites are rotated by tide and wind. Access requires a stay at Heron Island Resort (or the University of Queensland research station).