Vertigo

The name describes the view: a wall that falls away beneath your fins into featureless blue while gray reef and blacktip sharks circle within arm's length. Operators have long used this corner of the western barrier for shark dives, and years of provisioning history mean the residents approach boats and divers with unnerving confidence — briefings cover hand positions for a reason. Even on quiet days a dozen sharks may attend, with dogtooth tuna and trevally cruising deeper. The clarity of the open Pacific gives the whole encounter a floodlit quality that channel dives on Yap cannot match.

その瞬間のために: Gray reef and blacktip sharks at close quarters; exceptional outer-reef visibility; the sheer drop that named the site.

地形: Steep outer-reef wall dropping from a shallow lip into deep blue water

流れ（カレント）: Usually gentle on the wall; surge over the reef flat in swell.

エントリー: Outer-reef site near the northwest channel mouth; enter on the wall and settle along the lip.

危険生物・リスク: Bold, close-approaching sharks; an unforgiving drop-off for buoyancy lapses; surge on the lip in swell.

保全: Sharks here are habituated to boats — keep hands tucked, follow the guide's positioning, and let the animals set the distance.

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）。