The Rooney Point snail mounds are one of the most unusual dive sites in Queensland. Marinelife.org.au describes a field of brown rocky mounds, each several metres across, built by vermetid snails – worm-like molluscs that cement their tubes together – sitting in a shallow depression off Rooney Point, the north-western tip of K'gari. The mounds were identified in 1988 and are rarely dived.

Each mound is riddled with holes, ledges and crevices, making it a miniature reef on the sandy floor of Platypus Bay. Marinelife.org.au lists wobbegongs, sea snakes and moray eels in the mounds and trevally, snapper, coral trout and other pelagic fish around them. The biological rarity is the main draw: few divers have seen vermetid structures of this scale, and they are of scientific interest as well as a fish habitat.

Depth defines the dive: 28-29 m at low water and 30-32 m at high water. Bottom time on air is short, so nitrox and careful planning are recommended, and the site suits experienced deep divers. The long run from Urangan – up the full length of Hervey Bay – means a calm day, a capable boat and an early start.

Rooney Point is also a significant area for loggerhead turtles, and a go-slow zone applies from 15 October to 30 April, requiring vessels to stay off the plane. Humpback whales rest in Platypus Bay during the July-October migration, which can add surface encounters on the trip.

This is an expedition-style dive for experienced divers with local knowledge and their own boat or a club charter.

Launch at Urangan Boat Harbour and run north up Hervey Bay along the western side of K'gari to Rooney Point – roughly 60 km, allow 1.5-2 hours in a trailer boat in good conditions. Marinelife.org.au gives the position as 24°45'4.51"S 153°5'38.87"E. Note that the area is a go-slow zone for turtles from 15 October to 30 April – vessels must be off the plane.

Drop a shot on the mounds; there is no mooring.

Platypus Bay is sheltered from south-easterly ocean swell by K'gari, but the long run from Urangan is exposed to wind chop across Hervey Bay – aim for winds under 15 knots. Depth is 28-29 m at low water and 30-32 m at high water; dive at slack water to limit current on the mounds. Visibility varies with plankton and runoff; winter is best.

From 15 October to 30 April the area is a go-slow zone to protect loggerhead turtles.

Descend the shot directly to the mounds, explore two or three nearby mounds looking into holes and ledges for wobbegongs, morays and sea snakes, and keep a close watch on no-deco time. Return to the shot, ascend and complete a safety stop; use an SMB if you lose the line.

Nitrox (EAN28-30) recommended; conservative profiles given remoteness.

No regular operator – private boat or club charter; Hervey Bay Dive Centre lists 'Roonies' among regional sites.