The Quarantine Station occupies the sheltered western slope of North Head, where from 1832 to 1984 ships suspected of carrying disease landed their passengers to wait out their isolation. The heritage precinct is now the Q Station hotel and museum within Sydney Harbour National Park, and its beach and wharf front one of the calmest bays on the harbour. The dive has two parts.

Inside the bay, sand and seagrass at 3–6 m stretch between the wharf piles and the old mooring blocks, and this is macro country: White's seahorses on the weed and net remnants, pipefish, stingarees, cuttlefish, octopus and, at night, a great deal more. Around the northern point the fringing reef of boulders and kelp drops to 10–16 m, and here the growth becomes recognisably North Head – sponges and sea tulips under the ledges, blue groper, old wives, leatherjackets, sea dragons on the sand line and, in late summer, the subtropical fish that Sydney Dive Charters notes as a feature of its 5–16 m boat dive here. The Centurion clipper, wrecked in 1887, lies in 18 m off Quarantine Point a little further round and is often combined with this site by boat.

Historic debris from a century and a half of quarantine shipping litters the bottom and is protected. Access is the complication. The precinct is managed and the beach is not a public road-end; divers arrive by shuttle from the Q Station car park or by boat, and arrangements for gear, parking and after-hours entry should be confirmed in advance rather than assumed.

Once in the water it is a beginner-level, current-free dive, excellent at night, and one of the very few Sydney sites that combines seagrass critters and sponge reef in one swim. It suits new divers, photographers and history-minded divers; it lies inside the North Harbour Aquatic Reserve.

Shore access is through the Q Station precinct in Sydney Harbour National Park: from Manly follow Darley Road and North Head Scenic Drive to the Q Station gate (about 3 km), where visitor parking and a shuttle bus down to the wharf precinct are available; access, parking and gear-carrying arrangements change and must be checked with Q Station in advance, and after-hours or night access generally requires a booking. From the wharf it is a short walk to the beach for a sand entry, with a rock platform alternative at the northern end depending on tide. By boat it is 5–10 minutes from Manly Cove or Little Manly ramp; anchor on the reef off the northern point in 8–12 m.

Exit at the beach.

One of the most sheltered spots on the harbour, facing west-south-west behind North Head: diveable in north-easterly gales and in most southerlies, with only a very large southerly swell putting surge on the outer reef. Tidal movement is slight in the bay but picks up on the northern point. Visibility is 5–12 m and drops sharply after heavy rain when the harbour runs brown; the best water arrives on winter westerlies and on the top of a flood tide.

Ferry wash and small-boat traffic are the constant factor, especially on summer weekends when the bay fills with anchored boats.

From the beach, swim out over the seagrass and sand at 3–6 m looking for seahorses and pipefish on the weed and the old wharf piles, then follow the fringing reef north-east around the point where boulders and kelp drop to 10–16 m with sponges and subtropical fish. Turn at half air, return along the reef and finish over the seagrass; surface only close to the beach. Night dives stay in the bay.

Sydney Dive Charters lists Quarantine Station (5–16 m fringing reef) among its boat sites and runs it from Little Manly; Dive Centre Manly and local clubs organise occasional shore and night dives through Q Station, including Northern Beaches Ocean Festival club events. Independent shore access depends on Q Station permission.