Bajo Alcyone

Located in the late 1980s by Jacques Cousteau's team and named for their turbosail ship Alcyone, then made famous by decades of shark research, Bajo Alcyone is the purest expression of what Cocos does. The seamount's summit levels off around 27 m; divers pull themselves down the mooring line through the blue, wedge in among barnacle-crusted rocks, and wait. Barberfish rise to meet incoming scalloped hammerheads, and on the good days the school builds overhead until it dims the surface light. Marbled rays sail past like flying carpets, whitetips thread the rocks, and the drifting deco stop in open water regularly produces silkies and, in season, a whale shark.

その瞬間のために: The archetypal hammerhead cleaning station, marbled rays, blue-water safety stops with silkies

地形: Flattened volcanic summit at 25-30 m dropping into deep water

流れ（カレント）: Descend the line, get behind rock, stay low; the current is what delivers the sharks.

危険生物・リスク: Depth plus current plus blue-water ascent - a dive to plan conservatively, 36 hours from help.

保全: Cocos Island National Park; no gloves on the reef, no contact, ranger-monitored moorings.

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）。