d100 = 1
The players come across a shipwreck. The ghost of the ship's captain beckons them to find his lost treasure on the ocean floor. Will they risk encountering underwater monsters to claim it?
D1 Underwater Random Encounters
D&D 5e · 100 scenarios · Roll d100 → roll D1
A complete D&D 5e random encounter table for underwater scenes. Roll a d100 to pick a set, then roll a D1 to pick a scenario within that set — 100 unique D&D encounter scenarios in total. Every scenario is system-neutral and runs on either the 2014 Player's Handbook or the 2024 D&D revision. Pair each scenario with a stat block from our D&D monsters catalogue and you have a session-ready encounter in under a minute.
How to roll this table
- When the party enters a underwater, roll a d100.
- The result (1–100) is your scenario. Read it out and run with it.
The D1 Underwater encounter table
d100 = 2
A school of bioluminescent fish surrounds the party, forming intricate patterns that seem to convey meaning. Suddenly, the fish scatter as an eerie glow emanates from a nearby cave. Within, the players discover an ancient underwater library guarded by a spectral librarian who demands they solve a riddle to access the knowledge. They have 10 minutes to decipher the glowing runes before they lose the opportunity to glean invaluable information about the region.
d100 = 3
You see a single mermaid singing a hauntingly beautiful song, luring unsuspecting sailors to their doom. As the players approach, the mermaid may become hostile or join them on their journey.
d100 = 4
A small underwater geyser releases a burst of warm water.
d100 = 5
The players find a colony of merfolk who are sick and dying from a mysterious disease. They ask the players to retrieve a rare herb from the depths of the ocean to cure them. But the herb is guarded by a powerful sea dragon.
d100 = 6
A lone seahorse clings to a piece of seaweed.
d100 = 7
A water elemental has been causing chaos in the ocean, and the players are hired to stop it. However, they must first navigate through treacherous waters and underwater currents to reach the elemental's lair.
d100 = 8
The party sees a small group of mermaids who are exploring the seafloor and looking for food.
d100 = 9
A group of aquatic elves that have been shipwrecked for weeks and have run out of water.
d100 = 10
A ship with a broken mast is seen in the distance. It appears to be badly damaged.
d100 = 11
A giant squid appears, seemingly friendly and offering to let the players ride on its back. However, as they ride deeper into the ocean, the players realize the squid is leading them into a dangerous and deadly territory.
d100 = 12
You come across a small patch of bioluminescent algae glowing softly.
d100 = 13
A group of mermaids in a large school are swimming toward an island. They are carrying food for their king.
d100 = 14
A small battle between a group of merfolk and kuo-toa occurs in the water. Players can try to help or run for their lives.
d100 = 15
The players are attacked by a group of 1d20+20 crabs. The crabs are Level 1 monsters.
d100 = 16
A group of sharks are eating a living body. The person is still alive but will die soon if not rescued.
d100 = 17
The players meet a group of sea druids who are trying to bring balance to the sea by calming a raging storm. The druids seek the players' help in locating a powerful artifact that can help them in their mission.
d100 = 18
A shipwreck has become the lair of monstrous sea serpents. This wreck also holds a cursed artifact, which the players must retrieve without alerting the serpents, or alternatively, they might challenge and defeat these mighty guardians.
d100 = 19
The party happens upon a colossal sunken statue of a long-forgotten sea deity. Coral and barnacles cover its surface, but a shimmer catches the eye—an intricate gemstone embedded in the statue’s forehead. As they approach, the ground around the statue starts rumbling, and the gemstone begins to pulse ominously. They have 15 minutes to either remove the gem or retreat, as a massive stone guardian will awaken and attack.
d100 = 20
Rocks are coated in slippery, green algae.
d100 = 21
A group of squids are attacking a group of merfolk and trying to eat them.
d100 = 22
A school of sharks is attacking a ship.
d100 = 23
A group of Mermen fishing and singing sea shanties. They offer the players some freshly caught fish and join in on a song if they're friendly.
d100 = 24
A shipwrecked sailor is stuck on a rock. He will attack the party if they approach.
d100 = 25
The players see a group of kobolds fighting with a group of humans. The humans are trying to force the kobolds to stop attacking their ships.
d100 = 26
A group of sea dwarves offer the players a ride on their submarine, but they must defend the submarine from an attack by a group of sea dragons.
d100 = 27
A manta ray soars gracefully overhead.
d100 = 28
A group of merfolk are swimming through the water. One of them has a large scar on their back. If the players talk to them, they will say that they were attacked by a group of hostile merfolk led by a sea giant.
d100 = 29
2d20+10 Crab-Men that are all above level 1. If the party encounters them, they will be above level 1.
d100 = 30
You come across an underwater rift with geothermal activity.
d100 = 31
A shipwreck has become the lair of monstrous sea serpents. This wreck also holds a cursed artifact, which the players must retrieve without alerting the serpents, or alternatively, they might challenge and defeat these mighty guardians.
d100 = 32
Drift algae form tangled mats on the water’s surface.
d100 = 33
Fish scales reflect a brief flash of light.
d100 = 34
A giant whirlpool suddenly appears in the ocean, threatening to suck the players and their ship down into its depths. They must use all their skills to navigate out of the whirlpool or find a way to calm the angry sea goddess who created it.
d100 = 35
A trail of sand marks the slow path of a sea urchin.
d100 = 36
A curious seal trails you for a while before losing interest.
d100 = 37
A group of merfolk are on a quest to discover the source of recent earthquakes in the area.
d100 = 38
The players come across a group of merchildren playing hide and seek. They ask the players to be the seekers and promise a reward if they find all of them.
d100 = 39
A group of 4d6 giant lobsters attack.
d100 = 40
1d4 magical sling stones with a note. The note reads "PREPARE TO BE GRILLED!!"
d100 = 41
A group of starfish lays clustered on a rock, their arms interlocking.
d100 = 42
A ship is sinking! The ship is manned by pirates and has a chest on board worth 1d10x1000 gold pieces. The pirates will abandon ship, leaving the chest behind if threatened.
d100 = 43
Sponges of various shapes and colors dot the landscape.
d100 = 44
While exploring a sunken ship, the players find a powerful magical compass that can guide them to a hidden treasure. However, the compass is cursed and leads the players to a dangerous underwater tomb. They must break the curse and defeat the tomb's guardians to retrieve the treasure.
d100 = 45
A school of fish swims by. They are followed by a giant whale swimming through the water with them.
d100 = 46
An abandoned ship is stuck on some rocks, and its crew has been transformed into merfolk. They ask the players to help them break the curse.
d100 = 47
The players encounter a reef made of living coral, which is home to a powerful druid who controls the creatures of the ocean. But as they approach the reef, they realize that the druid is not what they expected. Will they befriend or battle the druid and its natural guardians?
d100 = 48
A large coral reef shaped like a face is encountered. It has large, sunken eyes and is filled with a small school of fish, who seem to be looking out of its eyes.
d100 = 49
The players encounter a shimmering bubble leading into an air pocket hidden within a submerged cavern. Inside, they find a despondent water nymph whose tears can heal any ailment. However, her sorrow is causing the cavern to flood rapidly. They have 20 minutes to find a way to console her and stop the flooding before the cavern fills completely, drowning them in the process.
d100 = 50
Players come across a treasure chest underwater. It is actually a trap.
d100 = 51
Players see a giant blue octopus using its tentacles to manipulate and rearrange coral reefs. If approached, it will offer the players a prize for finding an underwater artifact.
d100 = 52
The players find themselves in the middle of a battle between two sea monsters - a giant kraken and a colossal leviathan. Will they choose a side or try to flee from the chaos?
d100 = 53
A large coral reef shaped like a face is encountered. It has large, sunken eyes and is filled with a small school of fish, who seem to be looking out of its eyes.
d100 = 54
Players are accosted by a group of sharks. They want the players to stop attacking their pod.
d100 = 55
A beds of scallops snaps closed at your approach.
d100 = 56
1d6 sharks are eating something on the deck of the ship at the bottom of the sea. If player investigate by looking through a ship window, they will see a giant squid lying under a pool of blood.
d100 = 57
A spiral shell catches your eye as it glints in the sunlight.
d100 = 58
The group encounters a pod of dolphins that lead them to an enchanting underwater garden. At the center is a radiant flower that can enhance magical abilities. However, once the flower is touched, a force field begins to collapse, requiring them to find and deactivate five runic stones within 15 minutes, or the field will implode, destroying the garden and everything in it.
d100 = 59
A giant Whale, a neutral giant whale with an 18 foot long mouth that is 10 feet wide. It has 1000 hit points and an attack that deals 10d10 damage with a bite and a 10d10 damage with a head butt. The whale is used to ram things.
d100 = 60
A group of humans, 2d6+2 kobolds, and 2d6+2 merfolk are all fighting over a sunken treasure chest.
d100 = 61
A quick rain shower creates a rippling effect on the water's surface.
d100 = 62
A massive underwater whirlpool uncovers a portal to an ancient, submerged city. The city is guarded by water genasi who believe the adventurers are invaders. The players must navigate the ruins and decipher ancient texts to uncover the city's secrets.
d100 = 63
A mermaid trapped in a fishing net, she will beg for the players to free her or else she will drown. But as they approach, they will be ambushed by a group of sahuagin.
d100 = 64
A sea witch offers to give the players gills so they can breathe underwater, but in return, they must retrieve a rare ingredient for one of her spells from a dangerous underwater cave.
d100 = 65
The players come across a school of giant jellyfish, but something seems off about them. They are actually illusions created by a group of clever kelpies looking for unsuspecting prey.
d100 = 66
The players are attacked by a group of 2d20 crabs. The crabs are Level 1 monsters.
d100 = 67
A kraken is thrashing wildly in the water, fighting off a group of sahuagin who are trying to steal its treasure. Who will the players side with?
d100 = 68
A school of sharks are swimming away from a place of loud music. If the players swim to the sound, they will see a cave at the bottom of the sea. Inside the cave is a merfolk musician playing music that is so loud it will stun anything living within earshot if they do not make a saving throw.
d100 = 69
A crab wave at players with one of its claws.
d100 = 70
The players are invited to a grand underwater ball hosted by a wealthy merfolk family. However, it turns out the family is cursed and the party must find a way to break the curse before midnight.
d100 = 71
The players come across a school of giant jellyfish, but something seems off about them. They are actually illusions created by a group of clever kelpies looking for unsuspecting prey.
d100 = 72
In the distance, a giant seahorse approaches, seemingly friendly. But upon closer inspection, the players realize it has been enchanted and controlled by a powerful sea witch. Can they break the spell and save the creature?
d100 = 73
A player brushes a patch of stinging sea anemones.
d100 = 74
A pod of 3d8 hippocampi swim past the players, fleeing from a gigantic sea cat that sees the players as a potential meal.
d100 = 75
A ship is sinking with a horrible captain on board.
d100 = 76
A group of mermaids are going to ambush the players. They will use their powers of charm.
d100 = 77
The players are invited to a grand ball hosted by a powerful sea witch. But as the night goes on, they start to realize that the witch has some dark, sinister plans for them and they must find a way to escape before it's too late.
d100 = 78
The players see underwater fungi growing on a dead tree.
d100 = 79
A mysterious underwater cave holds a portal to another dimension. The players must decide whether to enter the portal and face the unknown dangers or leave it be and continue on with their journey.
d100 = 80
The players encounter a group of friendly merfolk who are seeking help in retrieving a valuable magical artifact that was stolen from their village by a powerful sea witch. The witch will not give up the artifact easily, and the players must come up with a clever plan to retrieve it.
d100 = 81
A group of dolphins playing a game of fetch with a sunken treasure chest. If the players join in, they may win some valuable loot, but they may also attract the attention of larger and more dangerous sea creatures.
d100 = 82
As the players swim deeper into a vast coral reef, they encounter a colony of 3d6 merfolk. The merfolk are embroiled in a territorial dispute with a rival group and seek the adventurers' aid in diplomacy or combat. In return for their help, the merfolk promise rare and precious underwater treasures.
d100 = 83
A ship is on fire.
d100 = 84
The party sees a group of merfolk who are hungry and are searching for food. They will attack if the party comes between them and the food.
d100 = 85
The players encounter a peaceful tribe of aquatic elves, but they are being terrorized by a group of vicious sahuagin. Will the players help defend the tribe or let them handle it on their own?
d100 = 86
It's mating season for the merfolk and their singing and dancing lure the players into joining in. But as the festivities come to an end, the merfolk reveal their true intentions - to sacrifice the players to their sea god.
d100 = 87
As the players swim deeper into a vast coral reef, they encounter a colony of 3d6 merfolk. The merfolk are embroiled in a territorial dispute with a rival group and seek the adventurers' aid in diplomacy or combat. In return for their help, the merfolk promise rare and precious underwater treasures.
d100 = 88
A group of sea trolls have made their home in a sunken temple and are using it to summon a powerful sea god. The players must stop the ritual before it's too late.
d100 = 89
You find a broken piece of pottery lying half-buried in the sand.
d100 = 90
A simple net, torn and abandoned, floats aimlessly.
d100 = 91
Floating seaweed curls around a player's leg.
d100 = 92
The players come across a group of sea elves who are on a mission to stop a group of evil warlocks from summoning a powerful sea demon. The players must team up with the sea elves and defeat the warlocks before it's too late.
d100 = 93
A group of 4d6 giant lobsters attack.
d100 = 94
All around you, you see floating debris from a shipwreck. As you approach, you realize that the wreckage is being guarded by a school of aggressive and territorial merfolk who are not keen on sharing their loot. How will you navigate this encounter?
d100 = 95
Fanged worms wriggle amongst the corals.
d100 = 96
The players come across a shipwreck and inside, they find a group of air-breathing creatures who have been stranded in the underwater wreckage. The players must find a way to help the creatures escape or risk losing them to the depths forever.
d100 = 97
A ship is sinking and people are jumping off it into the water but they are being killed by the creatures below the water surface
d100 = 98
A lionfish watches you from a coral outcrop.
d100 = 99
A small skeleton is seen, standing up against a nearby coral reef. When the party approaches, it dissolves into limestone.
d100 = 100
A sea turtle swims lazily by, uninterested in the players.
Use this table with the rest of Doungim's D&D 5e toolkit
A random encounter scenario is just the start of a scene. Pair it with a creature from our D&D 5e monsters catalogue (3,000+ monsters with full stat blocks), an NPC from our pre-built D&D NPC roster, a spell from the D&D 5e spell list, and a reward from the D&D magic items catalogue — and you have a full one-page session ready to drop on your D&D 5e or 2024 party.
Other dice tiers for the underwater: D4, D6, D8, D10.
Want a different setting? Browse all 41 D&D encounter locations — from arctic plains to elemental planes, every D&D 5e location has its own table on Doungim.