Underwater Encounter Locations for Dungeons and Dragons 5e

"A sunken island with strange rampant seaweed. It is surrounded by kelp and a strong current forces swimmers down to it."

Tables for Wilderness, Semi-Civilised and Unusual Underwater locations. Result is from Underwater Unusual Locations.

[Photo by Scott Webb on Unsplash]

Underwater Encounter Locations

Under the sea waves is a world of kelp forests, haunted shipwrecks and coral reefs. Encounters might take place among seaweed gardens, murky trenches, sunken islands or undersea temples.

There is a 5e Underwater random encounter generator at ChaosGen. And a separate tool for encounter locations including Underwater.

There is also a pdf of these and more tables at the DM's Guild as Underwater Encounters.

Underwater Encounter Tables - creatures | locations | non-combat | enhancements

Underwater Wilderness Locations

d8+d12	Underwater Wilderness Locations
2	An ugly crevasse in an area of black kelp (near a permanent maelstrom)
3	A shallow trench on a sunken island and a wide sea cave entrance (it is touched by druidic magic)
4	A sparkling canyon (there are several sea flowers)
5	An area of dead coral (nearby is a mound of shells)
6	A rock reef by a patch of sea mushrooms (there is the corpse of a sea hag)
7	A shallow trench and a dying kelp garden (close by is a shipwreck)
8	An area of sea anemones (close by is a pile of rocks)
9	A patch of bright sea grass surrounded by shells (there is a harmless group of seahorses approaching)
10	A narrow chasm and a algae-covered rock (a strong current flows through the area)
11	A pile of red seaweed by a deep hole (there is a harmless group of fish approaching)
12	A bed of kelp with a mound of dead seaweed (there are a few unusual rocks)
13	A glowing sea cave entrance (many coloured lights are approaching)
14	An algae-covered rock and a patch of edible seaweed (nearby are a few underwater cave entrances)
15	A meadow of pink sea plants (there is a mass of rotting bodies chained together)
16	A pair of sea cave entrances (they are watched by a ghost)
17	An area of white sand littered with shells (the area is disguised by a hallucinatory terrain)
18	An undersea mountain (a forceful current pulls creatures downward)
19	A broken cliff by a patch of shells (someone has left a net)
20	A skeleton of an ancient sea titan (it is associated with octopi)

Underwater Semi-Civilised Locations

1d8+1d12	Underwater Semi-Civilised Locations
2	A sunken temple to a power of strength. There is a garden of colorful seaweed (there is a stationary pocket of air)
3	A carved monument with lawns of ornamental sea grass (there is a programmed illusion here)
4	A line of statues surrounded by rock (nearby is an ornate tomb)
5	A coral-carved hall with a patch of sea anemones (the area is associated with a magical tentacled monster)
6	A pillar of stone surrounded by sand (which is associated with whales)
7	A garden of pretty sea plants and an underwater cave entrance (a bright light is in the area)
8	A stone mosaic and a patch of cultivated seaweed (there is a sunken fishing boat)
9	An algae-covered shell mosaic near a seaweed garden (a forceful current pulls creatures upward)
10	A decorated shipwreck (nearby is a wide crevasse)
11	A coral-carved hall with a statue (it is protected by a sea spirit)
12	An edible kelp garden near a shell mosaic (by a sandy surface on coral)
13	An unusual line of statues and a pile of seaweed (many coloured lights are in the area)
14	A sparkling statue by a hidden carved underwater cave (there is an inquisitive group of crabs approaching)
15	A steep slope with a seaweed garden (there is a seaweed-covered barrel)
16	A statue of a sea deity (the marine wildlife has disappeared)
17	A cairn in a large pocket of air (nearby is an undersea mountain)
18	A sunken ruins with a kelp-covered shrine to a forgotten power (nearby is an oyster reef)
19	An area of living coral by a group of tentacled statues (there are a few clams)
20	A shrine to several deities made from a shipwreck (the area is blessed by a power of chaos)

Underwater Unusual Locations

1d8+1d12	Underwater Unusual Locations
2	A sparkling coral tomb of a storm giant built into an undersea mountain. Sometimes it shakes with rumbling noises.
3	A cave entrance lined with draconic runes. A dormant mechanism is located here along with many large bones.
4	Spear of the Ancients. A gigantic trident protrudes from the seabed. It is adorned with seaweed and used as a shrine to a hunting deity.
5	A beautiful structure built from bone and shells surrounded by a circle of pillars. A warrior from the surface died here.
6	A grand seaweed maze cursed by a powerful ghost. It is bound to wander its many paths and ask many questions of visitors.
7	Hulk of a sunken ship with a arcane metal device. There is a portal to the Shadowfell (or Limbo) which attracts strange creatures.
8	Garden of Above and Below. A strange garden of shells and objects from the surface. Merfolk come to admire it and add more things.
9	Several underwater cave entrances are home to powerful elemental magic. There are pockets of air with drawings and wall carvings.
10	An underwater crater with mounds of seashells and littered with debris. A maelstrom sometimes forms, tied to lunar phases.
11	Atop a ridge is an eroded line of giant statues, depicting members of a pantheon. Ancient magic lingers here, waiting to be tapped.
12	Hunger's Hill. A pile of disparate wrecks is lit by flickering colored lights that roam the area. Stories tell of undead sharks seen here.
13	A citadel of coral and stone decorated with shells and shiny objects. Aquatic elves often add more decorations and admire their artistry.
14	A system of tunnels and chambers is carved into dead coral. It acts as a palace for a marid and is linked to the Elemental Plane of Water.
15	A sunken island with strange rampant seaweed. It is surrounded by kelp and a strong current forces swimmers down to it.
16	Inn of the Sea Dragon. In a trench with magical wards, this structure is carved from coral. Travelers are found from many realms.
17	An unmoving giant golem stands by a wide abyss. A mosaic of sea plants and stone surrounds both, depicting a gilled humanoid.
18	A kelp forest of thick seaweed contains many oysters. Beside it sits a murky algae-covered gully. The area borders the Lower Planes
19	A stone arch stands over the remains of a kraken. Strange shapes and patterns appear and evolve in the brightly colored sand.
20	Eon Watcher. On a cliff-face is a timer of glass as tough as steel. It slowly fills with shells before resetting. Blessed by a sea deity.