Northern Arch
Depth is the range from the top of the site to its usual maximum; "recommended cert" is the mainstream-agency level operators usually ask for, not a legal rule. Currents and visibility change daily — treat everything here as planning ranges.
Northern Arch is the Poor Knights at their most vertiginous: a slot cut clean through the headland, walls sheer on both sides, the floor far enough down that clear water plays tricks on the depth gauge. In late summer short-tail stingrays assemble here, stacking in the arch in loose formations that can number dozens, with kingfish spiraling above them. Orca occasionally arrive to hunt the same rays, which empties the arch faster than any dive computer alarm. Even without the megafauna, drifting the walls among sponge and jewel-anemone color is a top-shelf dive; with them it becomes the story of the trip.
The moment you come for: Stingray squadrons in summer, sheer walls through the headland, occasional hunting orca
Topography: A deep vertical slot through the headland, walls dropping to about 40 m
Current: Flow funnels through the arch; crossing it can mean ducking into the lee of the walls.
Know before you splash
Hazards: Depth deception in clear water and funneled current; plan the dive shallower than the arch invites.
Conservation: No-take reserve rules apply; give aggregating rays space and never block the arch ends.
Nitrox: Worth it here — profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).
Who you'll meet
For photographers
Wide angle: ★★★★★ · Macro: ★★★☆☆ — editors' 1–5 rating of what this site gives each style of shooting