Fairy Grotto is one of Mike Ball's regular Osprey sites and features on its 4-night Osprey fly-dive, 7-night Coral Sea exploratory, Coral Sea Odyssey and Far Northern expeditions. Mike Ball describes a 'mountain range' of big coral bommies flanked by a steep wall dropping to more than 1,000 m, with small caverns and swim-throughs, and the same description is used across its itineraries.

The bommies form a line of peaks along the reef edge, separated by valleys and linked by swim-throughs. Their sides are cut with small caverns where light filters through, and the tops rise into the shallows. On one side of the range the wall plunges away into deep blue water, giving the dive an unusual combination of intimate structure and open-ocean scale.

The bommies carry soft corals, sea fans and whips, and the caverns are lined with encrusting sponges and sheltering fish: squirrelfish, soldierfish, sweepers and cardinalfish. Out along the wall, grey reef and whitetip sharks patrol, and dogtooth tuna, trevally and barracuda pass by. Anthias and chromis swarm over the bommie tops.

Fairy Grotto suits intermediate divers who enjoy exploring structure and want a quieter dive after the North Horn shark feed. The swim-throughs are short and open, but divers should mind their buoyancy and avoid fin contact with the delicate growth inside. It is also a good site for wide-angle photography, particularly of divers framed in cavern openings against the blue, and of the bommie peaks in afternoon light.

Liveaboard only. Mike Ball's Spoilsport runs 4-night fly-dive trips (depart Cairns Thursday evening, cruise north overnight via the Ribbon Reefs, cross to Osprey, fly back from Lizard Island) and 5–7 night Coral Sea expeditions; Spirit of Freedom visits Osprey on its 4- and 7-night itineraries, with a Cairns–Lizard Island flight connection. The open-ocean crossing from the Ribbon Reefs to Osprey (about 100 km) is made overnight.

Allow 2–3 days at Osprey on a typical trip. Fairy Grotto is on Mike Ball's 4-night Osprey, 7-night Coral Sea and Coral Sea Odyssey itineraries and is dived from a mooring.

Osprey is an isolated oceanic atoll about 350 km north-east of Cairns and roughly 100 km beyond the edge of the Great Barrier Reef, so every trip involves an overnight open-ocean crossing. Strong south-east trades (over about 25 knots, common June to August) make the crossing rough and can close the exposed eastern and southern walls; liveaboards then work the sheltered western wall and North Horn. Sep–Dec usually brings the lightest winds and visibility of 40 m or more.

Currents on the walls vary with tide and oceanic flow and can run strongly around the horns. Dec–Apr is cyclone season and trips can be cancelled or diverted to the Ribbon Reefs.

Descend among the bommies to about 20 m, work through the small caverns and swim-throughs, then visit the wall edge to look down the drop-off and out for sharks. Return over the tops of the bommies for a long safety stop.

Mike Ball Dive Expeditions (Spoilsport) – Osprey fly-dive, 7-night Coral Sea, Coral Sea Odyssey and Far Northern expeditions.