Rapid Horn is the southern tip of Osprey Reef, and because it faces into the south-east trades it is dived far less often than North Horn at the other end of the atoll. Spirit of Freedom describes a 1,000 m drift wall at the southern tip, dived in summer only, with dense fish schools, parrotfish and tuna. A ScubaBoard report from the Nimrod Explorer names 'Raging Horn' with two drift dives, probably the same site.

The structure is a reef plateau at the tip with a sheer wall dropping on either side. Current wraps around the horn and concentrates food, so fish gather in numbers on the plateau and along the edge: schools of trevally, fusiliers, surgeonfish and parrotfish, with dogtooth and yellowfin tuna, grey reef sharks and whitetips on patrol. The chance of hammerheads, silvertips and other oceanic visitors is higher here than on the sheltered western wall.

The dive is typically a drift along the wall, with divers covering long distances and relying on the tender for pick-up. The reef is exposed to swell, so coral on the plateau tends to be low and robust, while soft corals and fans grow on the wall below.

Rapid Horn suits advanced divers comfortable in strong current and blue water. It is a site to hope for rather than expect: only a summer calm makes it possible, and crews will favour the western wall and North Horn when conditions are marginal. When it is on, it offers some of the densest fish action at Osprey.

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. Rapid Horn is exposed to the south-east trades and is dived only in summer or on calm days, usually as a drift from a tender. It is rarely dived compared with North Horn.

Rapid Horn faces into the prevailing south-east trades and is generally dived only in summer, when the trades ease or winds swing north. Currents around the southern tip are strong and variable, so it is run as a drift with tender pick-up. Swell and wind over about 15 knots from the south-east rule it out.

December to April is cyclone season, and trips can be cancelled or diverted, so opportunities are limited.

Drop from the tender up-current of the horn, descend to 20–25 m on the wall and drift with it, watching the plateau above for fish schools. Keep a close eye on depth and current direction, ascend under an SMB and complete the safety stop in open water.

Spirit of Freedom – summer only, when weather allows; occasionally Mike Ball.