North Horn is Australia's best-known shark dive, and the reason many divers make the long trip to Osprey Reef. The site sits at the northern tip of the atoll, where a soft-coral-covered bommie and a natural coral-rubble amphitheatre at around 12 m lie at the top of a wall that plunges well over 1,000 m into the Coral Sea.

The shark dive is run as a controlled feed. Dive the World describes up to 26 divers sitting in a semicircle at about 12 m while a bait drum is released 10–15 m away; Mike Ball says 10–30 grey reef, whitetip reef and silvertip sharks typically attend, and silky sharks and the occasional hammerhead also appear. Marinelife.org.au records that feeds used baited milk crates. The sharks arrive quickly as the drum opens and circle closely before dispersing. Potato cod, red bass and dogtooth tuna join in. Mike Ball calls the site 'shark central'.

North Horn is also a superb wall dive in its own right. The bommie is draped in soft corals, fans and whips, the wall has ledges and caves, and the blue water beyond brings eagle rays, manta rays, yellow-tailed fusiliers, dogtooth tuna and even the rare sailfish. On good days visibility exceeds 40 m. Spirit of Freedom notes soft corals at 25–40 m and describes it as a natural amphitheatre on a wall of more than 1,000 m. A memorial plaque sits on the wall at about 32 m.

The feed is conducted by permitted operators under Parks Australia rules within the Coral Sea Marine Park. The Important Shark and Ray Areas assessment of Osprey Reef notes a monitoring receiver at North Horn, where operators sometimes attract and feed reef sharks. The dive suits divers with some experience in open ocean conditions.

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. North Horn is on every Osprey itinerary. Boats moor off the tip, and divers descend to a natural amphitheatre at about 12 m for the shark feed or drop onto the wall for a drift.

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. The North Horn mooring is exposed at the tip and can have current wrapping round from either wall.

For the feed, descend the mooring to the coral-rubble amphitheatre at about 12 m, kneel in the semicircle behind the guides and stay still while the bait drum is released 10–15 m away. After the feed, if gas allows, visit the soft-coral-covered bommie and the wall ledges at 25–30 m, then ascend along the wall for the safety stop.

Mike Ball Dive Expeditions (Spoilsport) – 4-night Osprey fly-dive, 5-night Coral Sea & Cod Hole and 7-night Coral Sea expeditions from Cairns, several a month; Spirit of Freedom – 4- and 7-night trips including Osprey, weekly. Both run the North Horn shark observation/feed dive.