Secret Caves is an Osprey Reef site that Spirit of Freedom describes as a great afternoon and night diving spot, with vertical and sloping walls, manta rays and barracuda. The caves that give it its name are cut into the reef face and are open enough to explore with a torch.

The walls alternate between vertical sections and gentler slopes, which gives divers a choice of depth and pace. The caves shelter squirrelfish, soldierfish, sweepers and crustaceans, and soft corals and fans grow around their entrances where the current delivers food. Out from the wall, manta rays sometimes glide past and barracuda schools hang in the blue.

At night the site changes character. Nocturnal animals emerge from the caves, including crabs, shrimps and lobsters, and parrotfish tuck into crevices to sleep in their mucus cocoons. Sharks hunt along the wall, and plankton attracted by torches brings in small fish. Because Osprey has flashlight fish at nearby Admiralty, it is worth switching torches off briefly in the caves to look for bioluminescence.

Secret Caves suits intermediate divers comfortable with a wall and with basic cave awareness; the caves are not deep penetrations, but good buoyancy and care not to stir up sediment are essential. It is a good choice for divers wanting a gentler dive after the drifts and shark action elsewhere at Osprey, and its caves reward slow, careful torch work.

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. Secret Caves is dived by Spirit of Freedom, typically in the afternoon or at night from a nearby 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 to 15–20 m on the wall, follow it past the caves (enter only open caves with clear exits), watch for mantas and barracuda off the wall, then ascend to the shallows for a safety stop. At night, stay close to the wall and the group.

Spirit of Freedom – 4- and 7-night trips including Osprey; afternoon and night dives.