The Underwater Tunnel is a tunnel found on Harmony Island under the Saradomin statue, accessed during the quest Great Brain Robbery. It's connected to the church on the island, which is barricaded by Mi-Gor's zombie crew during the quest. A fishbowl helmet and diving apparatus are required to enter. Ten level 49 zombie pirates can be found within. This is one of the few areas where the brine sabre's special attack, Liquefy, can be used, as it only works underwater.
Ancient Cavern • Ardougne Sewers • Clock Tower Basement • Eagles' Peak Dungeon • Elemental Workshop • Goblin Cave Mogre Camp (Port Khazard) • Observatory Dungeon • Temple of Ikov • Tower of Life Basement • Underground Pass • Waterfall Dungeon • White Wolf Mountain Caves • Witchaven Shrine Dungeon • Yanille Agility dungeon
Digsite Dungeon • Dorgeshuun Mines • Draynor Sewers • Dungeon of Tolna • Edgeville dungeon • H.A.M. Hideout • Lumbridge Swamp Caves • Saradomin Shrine • Stronghold of Security • Tunnel of Chaos • Varrock Sewers
Ape Atoll Dungeon • Dorgesh-Kaan South Dungeon • Dungeon (Player-owned house) • Entrana Dungeon • Evil Chicken's Lair • Grand Tree Tunnels • Jatizso Mines • Lunar Isle Mine • Miscellania & Etceteria Dungeon • Mos'Le Harmless Caves • Underwater Tunnel • Waterbirth Dungeon