Barren Island and its small neighbour Child Island mark the outer edge of the Keppel group, and they deliver the clearest water and some of the best coral diversity in the region. The standard 'deep site' is on the seaward face, where the reef descends in a series of ledges and terraces from about 6 m to 30 m. Large brain corals and boulder corals cap the upper ledges, and further down the walls are cut by tunnels, fissures and overhangs that shelter big grouper, greasy cod, barramundi cod and coral trout.

Sea fans and whips grow on the steeper faces and schools of fish hang in the current off the edge. Divers who have dived here describe more than 30 hard coral species on the upper slopes, and staghorn thickets in the shallows. Being further offshore, Barren attracts pelagics that rarely come into the inner bay: Spanish mackerel, tuna, cobia (black kingfish), trevally and barracuda, and occasional manta rays in winter.

Humpback whales pass close to the island between July and October. The island is part of a site cluster: One Bum Beach on the sheltered side is an easy fringing reef, and The Gulch runs through the channel between the two islands, so a day trip to Barren usually combines two quite different dives. Barren suits confident divers with Advanced certification or good experience, especially photographers after wide-angle scenes with better visibility than the inner islands offer.

Because of the long crossing it is not dived every week, so it is worth asking the operator early in a stay and being flexible about the day.

Drive 40 km (about 40 minutes) from Rockhampton to Yeppoon, then 7 km south along the Scenic Highway to Keppel Bay Marina at Rosslyn Bay Harbour, where there is free and paid parking. Freedom Fast Cats and Keppel Konnections ferries run to Great Keppel Island (Fisherman's Beach) in about 30 minutes; Keppel Dive & Water Sports picks up certified divers from the island. Barren Island is the longest run of the Keppel day sites: about 30-40 minutes by dive boat from Great Keppel, or 50 minutes by private boat from Rosslyn Bay across open water.

Boats anchor on sand in the lee of the island depending on wind; it is visited only in settled weather.

Keppel Bay is exposed to the prevailing south-east trades (strongest April-September) and to summer northerlies. Barren Island sits at the outer edge of Keppel Bay and receives clearer offshore water (15-30 m on good days) but also the full swell. It needs winds under about 15 knots and a small swell; dive the lee side according to wind direction.

South-easterlies over 15-20 knots make the crossing uncomfortable and close the seaward ledges. Currents strengthen around the headlands and between Barren and Child Islands on spring tides. Best July-October; summer northerlies and storm run-off reduce visibility.

Descend on the seaward side of Child Island to the top of the ledges at 10-12 m, then step down the terraces to 20-25 m, checking the tunnels and crevices for cod and grouper. Turn after 15-20 minutes and zig-zag back up across the ledges, finishing among the brain corals and boulders in 6-8 m for the safety stop.

Keppel Dive & Water Sports (PADI 5 Star, based on the Spit at Great Keppel Island next to Great Keppel Island Hideaway) runs guided boat dives to the Keppel sites most days, weather permitting, plus courses and Discover Scuba; site choice is made on the day according to wind. Private boats from Rosslyn Bay also dive here. Barren Island is usually run as a two-dive trip combined with One Bum Beach or The Gulch.