Shark Fin Reef

Shark Fin Reef runs like a half-submerged spine, its exposed crest suggesting the fin that named it, with two long faces of tilted granite slab sliding into sand past 30 m. The eastern side stacks hard-coral gardens and sweeping slab scenery; the west goes steeper and moodier. Blue-spotted ribbontail rays shuffle under ledges, garden eels stipple the deep sand, titan triggerfish excavate with their usual self-importance, and this southern corner remains one of the archipelago's better bets for a zebra shark flat out on the bottom. An unflashy, spacious dive that shows the Similans' scale without demanding anything exotic in return.

その瞬間のために: Kilometer-scale granite spine, rays and garden eels on the sand, southern-sector calm

地形: Tilted granite slabs and coral gardens dropping to sand

流れ（カレント）: Flow runs the length of the ridge and the dive becomes a one-way drift along whichever face is in the lee.

エントリー: A long granite ridge southeast of island 3, its crest breaking the surface; often the first dive of northbound itineraries.

危険生物・リスク: Length of the ridge can string groups out in current; agree on the drift plan before rolling.

保全: Park rules apply; give nesting titan triggerfish their cone of territory in the warm months.

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）。