Northern Arch

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.

その瞬間のために: Stingray squadrons in summer, sheer walls through the headland, occasional hunting orca

地形: A deep vertical slot through the headland, walls dropping to about 40 m

流れ（カレント）: Flow funnels through the arch; crossing it can mean ducking into the lee of the walls.

危険生物・リスク: Depth deception in clear water and funneled current; plan the dive shallower than the arch invites.

保全: No-take reserve rules apply; give aggregating rays space and never block the arch ends.

ナイトロックス: ここでは効果的です——このエリアのプロファイルは、ナイトロックスが無減圧潜水時間を有意に延ばせる水深帯にあります（適切なトレーニングを受けていることが前提です）。