Tracey's Bommie is one of the best-known sites on Flynn Reef and a favourite of Cairns dive guides. A large coral bommie rises from a white-sand seabed beside a pristine lagoon, its top within a few metres of the surface, and on its outer side the bottom falls away into deeper water to about 25 m. The bright sand reflects plenty of light onto the bommie, which gives the site a clean, open feel and makes it very photogenic.

The bommie's flanks are covered in hard corals with patches of soft coral, and several cleaning stations operate along it, where you can hover and watch cleaner wrasse and shrimp servicing coral trout, sweetlips and surgeonfish. A resident Maori wrasse often comes in close to inspect divers. The sand around the base is the place to look for blue-spotted lagoon rays, garden eels and goatfish, while giant moray eels occupy holes low on the bommie.

Cuttlefish hover over the coral, nudibranchs and flatworms can be found on the rock, and schools of unicorn surgeonfish, batfish and triggerfish drift past. On the outer drop the water opens up and reef sharks and trevally are more likely. At night Tracey's is excellent: painted crayfish emerge from the crevices, parrotfish sleep in mucus cocoons, and cuttlefish hunt over the sand.

The combination of modest depth, sheltered water and plenty of life makes it suitable for all levels, and the shallow top is good for snorkellers. Little Tracey, a smaller neighbouring bommie with its own mooring, is a separate site.

Boat access only. Cairns day boats leave from the Reef Fleet Terminal (1 Spence Street) and the neighbouring Marlin Marina on the city waterfront, with check-in between about 7:00 and 8:00 am; most operators run transfers from city and northern-beaches accommodation, and there is paid parking near the terminal. The run of about 57 km out through Trinity Inlet and across the lagoon to Flynn Reef takes around 80 minutes on a fast catamaran and noticeably longer on slower dive boats or into a south-easterly chop.

Tracey's is a regular Silverswift and Pro Dive Cairns mooring; Passions of Paradise uses the neighbouring Little Tracey mooring. Kit up on the way out and enter off the stern.

The prevailing south-east trade winds (typically 15-25 knots from April to September) are what limit Cairns outer-reef diving: above about 25 knots trips may be cancelled, and exposed eastern moorings are used only in light winds. Summer northerlies are gentler but make north-facing moorings choppy. Box jellyfish and Irukandji are present from about November to May (stinger suits on every dive), and the cyclone season runs November to April, when a system in the Coral Sea can close the reef for days.

Visibility drops after heavy rain and strong winds; spring is usually calmest and clearest. The lagoon side of Tracey's is sheltered in south-easterlies and it is a common choice when the weather sides of Flynn are rough; at night it is one of the more reliable liveaboard moorings.

Descend to the sand at the base of the bommie (12-15 m), circle it clockwise, and at the far side follow the drop-off down to 20-25 m for a short look before turning back. Ascend in stages up the bommie, checking the cleaning stations on the upper flanks, and do your safety stop on the top at 5 m.

Silverswift (Silverseries) – daily day trips, three dives, rotating between Flynn, Milln, Thetford and Pellowe; Passions of Paradise – daily sailing-catamaran day trips to Flynn moorings; Pro Dive Cairns – 3-day/2-night liveaboard, sites on Flynn, Milln, Thetford and Pellowe including night dives