Underground Water

Rivers and lakes that run through the rock under the ground, cold, clear and silent. In lamplight the water is so clear that it seems not to be there until a boot goes in; the only sounds are drips, the hollow rush of a hidden fall and the echo of a voice that carries too far. Blind white fish, pale shrimps and the strange salamander called the olm live in it, and feed on what the water brings down. Some passages can be followed by boat or by swimming; some feed the springs and wells of the land above, and townsfolk draw from them without knowing. Cavers fear the sump where the roof meets the water, the flood that rises after rain far above, and the cold that numbs a swimmer in minutes. The underground river of Padirac, in France, followed by boat beneath the plateau, is water of this kind.

Hear it

• By the river: Underground River (On Patreon, Guardian tier)
• By the lake: Underground Lake Shore (In the album RPG Ambiences Vol. 7)
• Dripping water: Underground Lake Dripping on Shore (On Patreon, Guardian tier)
• By boat: Rowboat on Underground River (On Patreon, Guardian tier)
• A waterfall: Underground Waterfall (In the album RPG Ambiences Vol. 7)

Adventure hooks

1. A girl dropped her doll down the well in the town square. A week later it came out of a spring three valleys away, dry, its hair freshly plaited.
2. A river under the hills can be followed by boat for days, and a merchant wants to use it to move goods beneath the border without paying tolls. His last boatmen came back after a week with their hair gone white.
3. Blind white fish live in a lake deep under the hills, and the hermit who feeds them every day says they are souls. He must go to his sister’s deathbed, and needs someone to take his place and keep the count.
4. The town’s wells have started to taste of salt. Somewhere under the ground a wall of rock between the sea and the fresh water has given way, and the water master wants it found before every well is lost.

Animals

• Olm (harmless, in colonies, day and night)

Creatures

• Chuul (a fight to fear, Challenge 4)
• Spirit Naga (deadly, Challenge 8)
• Aboleth (deadly, Challenge 10)

This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at https://www.dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License, available at https://creativecommons.org/licenses/by/4.0/legalcode.

To fish

Blind Cave Fish, Swamp Leech Cluster, Glowspine Eel, Myconid Raft, Sightless Crab, Thermal Vent Worm, Drowned Delver, Obsidian Shrimp, Abyssal Angler

Nearby biomes

Cave, Mine, Sea Cave

Open it in Biomes — MGS Toolbox