Roberts Shoal lies just east of the Cape Moreton lighthouse and is one of the most dramatic pieces of underwater scenery off Brisbane. The Adreno regional guide likens it to the landscape of a ruined cathedral, with arches, overhangs, caves and spires rising from sand at around 35 m to about 12 m below the surface. Most of the dive is spent around 20 m, weaving between the pinnacles and peering into the caves.

It is very similar in terrain to Brennan Shoal immediately to its north, and charter operators often describe the two together: pinnacles and big caves, generally calm in terms of current but exposed to swell. The fish life reflects the open-ocean position. Schools of large pelagic fish, including trevally, kingfish and mackerel, patrol the edges, and large wobbegong sharks are common in the caves and under ledges.

A giant cod has been reported at around 25 m. Sponges and soft corals coat the rock, and the cracks hold crayfish and moray eels. Visibility averages about 20 m.

Because it is further round the cape than Flinders Reef and needs a calm day, Roberts Shoal is dived less often than the bay-side sites and is usually reserved for advanced divers on special outer-reef days. It rewards good buoyancy and navigation – the arches and caves are the highlight, and it is easy to lose track of depth when exploring the spires. On a clear winter day with light winds, it is one of the best dives in the Moreton area.

Boat access only. Brisbane charters leave from Manly Boat Harbour (Brisbane Scuba departs from the corner of Royal Esplanade and Davenport Drive, Manly) or from Scarborough Boat Harbour on the Redcliffe Peninsula, crossing Moreton Bay and running out through the North West Channel past Bulwer and Comboyuro Point to the northern tip of Moreton Island. Allow roughly 75-90 minutes from Manly in good conditions.

Sunshine Coast operators run south from The Wharf, Mooloolaba, in about 45 minutes. Private boats typically launch at Scarborough or Bribie Island; the open-water crossing around Cape Moreton is exposed and should only be attempted in settled weather with local knowledge. Roberts Shoal lies just east of the Cape Moreton lighthouse, with Brennan Shoal immediately to its north.

Currents are usually minimal, but the shoal is exposed and large swells are possible. Any easterly or south-easterly swell over about 1.5 m makes it rough, and the area off Cape Moreton can be confused where the swell wraps around the headland. Best in winter on light westerly days; visibility averages about 20 m.

Descend on the main pinnacles at 12-15 m, work down through the arches and caves to about 20-25 m, keep an eye out for the giant cod near 25 m, then zigzag back up the spires for the second half of the dive.

Supercat Charters and Brisbane operators (Brisbane Scuba, Go Dive Brisbane) – occasional outer-Moreton days in calm conditions.