Flat Rock is the centrepiece of North Stradbroke Island diving: a low rocky island about 2.5 nautical miles north of Point Lookout surrounded by reef that falls away to around 35 m. It is a fully protected marine park zone with no fishing within a 1.2 km radius, and the difference that makes is obvious underwater. marinelife.org.au and Manta Lodge divide it into four sites – The Nursery, Shark Alley, The Bowl and Turtle Caves – which together offer something for every level of diver. On the shallower south-western side, The Nursery has coral gardens in 5-16 m with nudibranchs, turtles, wobbegongs and, in summer, leopard sharks.

Turtle Caves has caves and ledges with turtles, bull rays and pygmy devil rays. The Bowl drops from 10 to 34 m through coral formations with cod, groupers, turtles and white-tip and grey nurse sharks. And on the eastern edge, Shark Alley is the famous winter aggregation site for the critically endangered grey nurse shark, which gathers in two sandy channels between June and October; Manta Lodge notes that only about 500 remain on the east coast.

Across the complex, divers see schools of rays, eagle rays, barracuda, pelagic fish, octopus, moray eels and a wide range of tropical and subtropical reef fish. Flat Rock's combination of shallow coral and deep, sharky gutters, all within 15 minutes of Point Lookout, is why it ranks alongside Julian Rocks and Wolf Rock among the best subtropical dives on the east coast. Beginners can dive it safely at The Nursery, while advanced divers head for Shark Alley and The Bowl.

Drive to Cleveland (about 40 minutes from Brisbane) and take the SeaLink vehicle ferry or a passenger water taxi across to Dunwich on North Stradbroke Island, then drive about 20 km (25 minutes) east to Point Lookout. Manta Lodge & Scuba Centre at Point Lookout runs the dives, beach-launching its boats and reaching the Point Lookout sites in roughly 5-15 minutes. Brisbane operators (Brisbane Scuba from Manly, Gold Coast Dive Adventures from Runaway Bay) also run occasional day trips.

Flat Rock is about 2.5 nautical miles north of Point Lookout (around 10-15 minutes).

Flat Rock is exposed to the open ocean. South-easterly winds over about 15-20 knots and easterly swell over about 1.5-2 m make the moorings rough and create surge in the gutters; northerly winds also chop up the site in summer. Currents are usually minimal to medium but can be strong around The Bowl and the deeper edges.

Visibility ranges from 10 to 30 m and is best in winter. After summer storms and heavy rain it can drop to a few metres.

Operators choose the sub-site to suit conditions and experience: The Nursery for shallow coral and newer divers, Turtle Caves for caves and turtles, The Bowl for coral and big fish, and Shark Alley for grey nurse sharks in winter. Descend the mooring, follow the guide's route and do the safety stop on the line.

Manta Lodge & Scuba Centre (Point Lookout) – daily boat dives, weather permitting; Gold Coast Dive Adventures and Brisbane Scuba – occasional Straddie day trips and weekends.