The Gulch is the deep channel separating Barren Island from little Child Island, and when the tide runs it becomes the Keppels' best drift dive. The channel floor sits at around 25-30 m and the walls on either side are covered in small colourful invertebrates, sponges and tunicates, with dense forests of sea whips and large sea fans growing out into the flow. Small caves and undercuts along the walls hide cod and crayfish, and the constant water movement brings in big fish: grouper, barracuda, trevally and Spanish mackerel patrol the channel, eagle rays and stingrays cruise the sand, and manta rays are occasionally seen in winter.

The walls are also good for nudibranchs if you slow down in an eddy. At the end of the channel the drift spills out over Child Island's shallower coral gardens and boulder field, where swim-throughs among granite boulders and patches of hard coral make a relaxed finish and a comfortable safety stop. The Gulch is best treated as an advanced dive: descents are made into moving water without a line, depth is significant, and divers need to stay together and be confident with SMB deployment.

When the timing is right, however, it is an effortless ride and one of the most varied dives in the region, combining wall, invertebrate life and pelagic action in one pass. It is normally paired with the deep ledges on Barren Island or the gentle One Bum Beach on the same trip. Operators generally brief this as a group drift with a guide leading and a surface marker deployed, and they only run it when they are confident of the tide; if the flow is wrong the day switches to the ledges instead.

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. The Gulch lies between Barren and Child Islands, about 30-40 minutes by dive boat from Great Keppel or roughly 50 minutes from Rosslyn Bay.

It is dived as a live-boat drift: the boat drops divers at the up-current end of the channel and follows their SMBs.

Keppel Bay is exposed to the prevailing south-east trades (strongest April-September) and to summer northerlies. The channel funnels tidal flow between the two islands, so the dive is timed with the tide: a moderate flow gives an easy drift, while spring-tide peaks are too strong. Wind against tide in the channel creates steep chop; aim for winds under 15 knots and low swell.

Best July-October for visibility; summer storms and river run-off reduce it.

Drop in at the up-current end of the channel and descend quickly to 18-25 m alongside one wall. Drift with the flow, checking the small caves and the whip forests, and gradually ascend along the wall as you move through. Finish shallow on Child Island's boulder and coral gardens in 5-8 m and deploy an SMB for pick-up.

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. The Gulch is run occasionally as a drift on Barren Island trips when tides suit.