Western Rocky

Western Rocky, near the archipelago's southern edge, concentrates Mergui's character into one cluster of limestone islets. The centerpiece is a tunnel passing clean through the main rock, a torch-lit corridor where tawny nurse sharks rest in the recesses and lobster eyes glitter from the ceiling cracks; divers exit into blue on the far side feeling they have been let in on something. Around the islets, walls and boulder slopes hold tigertail seahorses, harlequin shrimp, ornate ghost pipefish, and frogfish in densities that keep macro guides busy, while trevally and rainbow runners work the outside water. Night dives here rank with the region's best.

その瞬間のために: The through-island tunnel with resting nurse sharks, elite macro walls, strong night diving

地形: Limestone islets with a through-tunnel, walls, and boulder gardens

流れ（カレント）: Current splits around the islets; the tunnel is dived on the quieter windows.

危険生物・リスク: A genuine overhead passage with surge on some tides; save it for days when the water agrees.

保全: The tunnel's residents tolerate polite traffic; lights out of eyes and no blocking of the exits.

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）。