Your Ultimate Guide for Running a Deep-sea Exploration Adventure
“Underwater Kingdom” by Silberius, CC Attribution-Noncommercial-No Derivative Works 3.0 License
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Moored at a scanty port along the waypoint atoll Avon, the illustrious galleon Aurora contrasts the dilapidated docks. Waves nuzzle her polished keel, goading her back to sea. To the melody of the whistling wind through the rigging, a motley ship crew passes barrels, chests, and goods to the longshoremen, eager to reap rewards for their arduous haul. Sea birds sing praises to the rare blue cloudless sky. Paltry shops, taverns, and supervisory structures—erected haphazardly to accommodate the increase in trade since Pearl Island boomed—line the rocky shore.
Your players have found passage to this small island to begin their contract with the Aurora’s deep-ocean exploration crew.
What You’ll Get in This Article
- Galleon ship stats, map, and description
- Captain NPC description and stats block
- Call to Adventure for players
- Ship Crew Positions, Descriptions, and Motivations
- Methods for Breathing Underwater, including races, classes, magical items, spells, and non-magical items
- Encounters: Environments, Scenarios, Adventure Hooks, Monsters with CR levels
- Treasure Examples
- Underwater Combat Rules and Considerations
- Subplot Inspiration
- Additional Resources
The Aurora
Skillfully crafted from fine Great Oak, the Aurora is as proud a galleon as she is robust. Three masts stand sentinel over a gleaming deck.
The steady bowsprit shepherds the rest of the vessel like a compass needle guiding true. Her tenacious sails eagerly challenge the winds.
“Ship” by MaiLy-Painting, CC License
Note: This ship is varied slightly from the Galley contained in the UA article. Use the following guidelines instead of what is contained in the PDF when applicable. Otherwise, use the Galley’s stats, actions, and weapons for your adventure.
Galleon Map from 2MinuteTableTop, CC License
- 60 crew required
- 30 passengers allowed
- 100 x 25 feet
- Cargo capacity: 120 tons
- Special ability: Great Oak produces warmth, so it’s never cold on the ship.
- Travels 4 miles per hour
Captain Ellis
A round chin and a bulbous nose rest below soft, topaz eyes. Billowing, crinkled eyelids give the captain a grandfatherly expression under tufty white eyebrows, matching the girth of his thick beard and sparse hair.
His barrel-chest guiding the way, the captain strides with an air of assurance that inspires crewmen under his purview.
Burly Captain Ellis accepts all capable workers and directs his crew with a few unbending rules: Stealing gets you thrown overboard; payment is received upon docking according to your position; on the High Seas; we only survive if we work together; the Captain is the ultimate judge.
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Captain Ellis
Medium humanoid, neutral alignment |
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Armor Class: 14 (studded leather) |
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Skills: Acrobatics +7, Athletics +9, Insight: +6, Vehicles (Water) +10
Stealthy Knife: Once per turn, an attack made with his Stealthy Knife receives an additional 2d6 Sneak Attack bonus. Actions
Multiattack: Captain Ellis makes three attacks: two with his rapier and one with his Stealthy Knife. |
Your Players: Deep Sea Divers
Your players have been contracted to undertake deep sea exploration endeavors. This can include treasure hunting, research gathering, exploration, cleanup, and more.
Because this is a team-specific campaign, players should have the same crew position so that they go on adventures together. Each player can have his or her distinct role in the team—underwater navigator, lookout, lead swimmer, research analyst, etc.—based on character strengths and build.
“Divers” by Creative-Games, CC License
Crew Positions and Possible Motivations
The Aurora is staffed by a ragtag group of diverse men and women of all races.
When assembling the Aurora’s crew, consider the following positions and their possible motivations. Build unique personalities for your crewmen, as your players will be interacting quite a bit with them throughout the campaign.
The more your players can explore the ship and crew, the more intrigue, interest, and enjoyment you can weave into your story.
Cabin Boy by Ralph Hedley
- Artillery Master: developing new tech for underwater weaponry, paid really well, brother to captain, looking for trophy kill, seeking ideas of weaponry from new societies.
- Boatswain (repairer): good pay, smuggler who built a secret compartment on the ship, looking to escape authorities from homeland.
- Cabin boy: adventure, paid job, hoping to move up and take a better crew role, stowaway turned crewmember.
- Captain: seeking wealth, in it for the adventure, to gain notoriety, one secret item he’s questing for, seeks trophy kill, seeks revenge, secret smuggler under ruse of explorer.
- Cartographer: paid by royals to map uncharted waters, paid to keep track of where the ship has gone for nefarious secret boss, is secretly marking off locations of where something is or isn’t (creatures, treasures, etc).
- Cook: adventure, paid job, wishes to learn a new trade in spare time, secretly a pirate?
- Divers: adventure, paid job, searching for something specific and personal.
- Doctor: interested in gathering medical methods and plants/materials from other societies/environments, searching for someone on another island enroute, love interest is on ship and she/he vowed to keep her/him alive.
- First Mate: interesting learning the ropes for his own boat/crew one day, hopes to commandeer this boat once captain dies mysteriously, owes the captain his life, was bought out of slavery by captain.
- Guard: paid job, secretly guarding one specific crew member, wants to steal a certain item once discovered.
- Linguist: interest in other humanoid species, disguised and planning to escape to new island to escape his capture, searching for way to decipher a secret scroll.
- Navigator: seeking adventure, beholden to another crew member, searching for a lost fabled island, escaping unruly past under new identity.
- Scientist: desire to gain knowledge, seeking adventure, hoping to acquire wealth, big breakthrough discovery.
- Shantyman (musician): gaining inspiration for ballads, interested in meeting interesting people, owes a favor, came upon ship running from something and stuck around
Additional Crew Members:
Lookout, Blacksmith, Scholar, Chronicler, Able Seamen (Sailors, Rowers), Infantry (Archers, Artillerist, Swordsmen), Unassigned personnel, Deck Monkeys (usually a young urchin), Passengers, Pets, Captives.
Means to Breathe Underwater
You can be as advanced or fantastical in your setting as you wish. Choose to require divers to play a water-breathing race or provide magical items that allow adventurers to breathe underwater. Spells can also be cast at a cost. You could also use technological means to breathe, like oxygen tanks or steampunk scuba gear, or let your players get creative in their methods for underwater exploration.
“Alone in the Deep” by RobCV, CC License
- Race features (Water Genasi, Sea Elves, Warforged, Merfolk, Simic Hybrid with Underwater Adaptation, Darfellan, Koalinth (goblinoid), any Seafaring race from 3.5e Stormwrack, Otterfolk, Trition from Volo’s Guide to Everything, modified Dragonborn, see additional races here and here)
- Class features (Barbarian Path of the Totem Warrior Aquatic Hunter homebrew, Druid Circle of the Moon, Warlock Gift of Depths invocation)
- Spellcasting (Wizard spell, Sorcerer spell, Druid spell, Artificer spell, Ranger spell)
- A potion, scroll, or spell of water breathing
- A polymorph spell or scroll (turn into sea creatures)
- A control water spell or scroll (create air bubbles for you to breathe)
- Cloak of the manta ray
- Cap of water breathing (Dungeon Master’s Guide)
- Necklace of adaptation
- Artificial aqualung. Include a series of ports/depots where the aqualungs can be refilled, if this path has been taken by other air breathers before
- A primitive submarine
Encounters
While we won’t provide maps here, we will give ideas for various locations your party can explore, possible encounters, and adventure hooks to include.
Random Underwater Encounters
“Shipwrecked” by umbatman, CC License
Page 116 of the Dungeon Master’s Handbook provides a table for random encounters underwater:
d12 + d8 Encounter
2 | Sunken ship covered in barnacles (25 percent chance that the ship contains treasure; roll randomly on the treasure tables in chapter 7)
3 | Sunken ship with reef sharks (shallow waters) or hunter sharks (deep waters) circling around it (50 percent chance that the ship contains treasure; roll randomly on the treasure tables in chapter 7)
4 | Bed of giant oysters (each oyster has a 1 percent chance of having a giant 5,000 gp pearl inside)
5 | Underwater steam vent (25 percent chance that the vent is a portal to the Elemental Plane of Fire)
6 | Sunken ruin (uninhabited)
7 | Sunken ruin (inhabited or haunted)
8 | Sunken statue or monolith
9 | Friendly and curious giant sea horse
10 | Patrol of friendly merfolk
11 | Patrol of hostile merrow (coastal waters) or sahuagin (deep waters)
12 | Enormous kelp bed (roll again on the table to determine what’s hidden in the kelp bed)
13 | Undersea cave (empty)
14 | Undersea cave (sea hag lair)
15 | Undersea cave (merfolk lair)
16 | Undersea cave (giant octopus lair)
17 | Undersea cave (dragon turtle lair)
18 | Bronze dragon searching for treasure
19 | Storm giant walking on the ocean floor
20 | Sunken treasure chest (25 percent chance that it contains something of value; roll treasure randomly using the tables in chapter 7)
“Volcanic Terrain” by xxxsof, CC License
Ideas for Environment: Lava pools. Flowing magma underwater. Caverns throughout. On an island or free-standing. Active or semi-active. Above or under water. Secret hiding place? Once the kingdom of a long-passed ruler?
Adventure Hook: The Captain’s reliable confidant in a bustling island tavern relays whispers he’s heard from members of the local cult who have discovered the approximate location of the fabled Ark of Ba’althazar. This artifact could sell for a pretty penny, or maybe the Captain wants notoriety for his discovery.
Flavor: The Ark could be a myth, or it could be a box containing a demon or item that was supposed to be thrown into the volcano but somehow landed on a ledge nearby. Or maybe the Ark was already discovered by cult members and players will face an epic showdown.
Creature Encounters:
Cultist CR ⅛
Steam Mephit (fire water, maybe use with magma) CR ¼
Magma Mephit CR ½
Demon Bird CR 1 (homebrew)
Azer (fire elementals) CR 2
Cult Fanatic CR 2
Hell Hound CR 3
Fire Elemental CR 5
Fire Giant CR 9
Loot:
- Nuggets of Pearlsteel: “A strange metal crafted by secretive aventi metallurgists working near volcanic vents in the ocean floor, pearlsteel is gleaming, shining steel covered with a blue-white sheen like mother of pearl.” (StormWrack, page 128)
- Pearlsteel is very light in water and can be used to modify weapons or create armor that are more effective underwater.
- Slashing and bludgeoning weapons created with Pearlsteel receive a -1 modifier instead of halving damage.
- Armor made with Pearlsteel receive a -5 to swim
- Armor created with Pearlsteel add 1000 gp to the sell price. Weapons created with Pearlsteel add 1500 gp to the sell price.
- Gemstones found in caverns
- Ingredients for Alchemy, Herbology, etc.
- Obsidian for armor/weapon creating
- Brazier of Commanding Fire Elemental
- Fire Giant Heart (alchemy/herbalism)
- Hell Hound Teeth (alchemy/herbalism)
- Hell Hound Hide (Leatherwork)
Polluted Waters
“Nymph in Dark Still Waters” by Flauen, CC License
Ideas for Environment: Pollution can make it hard or dangerous to explore/dive. Corrosive water can damage equipment or adapt monstrous creatures.
Adventure Hook: Once a well-travelled canal for trade, this passageway between islands has recently become foggy, oozy, dark, and dangerous. Many ships have tried to travel through, only to find themselves turning back and sailing around or disappearing. Your ship is outrunning a foe: possibly a storm, a pirate ship, or a destructive monster. The fastest way to flee is through the dangerous bog. Do you risk it?
Adventure Hook 2: Once a well-travelled canal for trade, this passageway between islands has recently become foggy, oozy, dark, and dangerous. The last ship to disappear was the Queen’s own fleet of merchant ships, forced to travel through in order to avoid a monstrous creature. Four ships full of goods and treasures untold never made it to the other side. The Captain is just bold enough to go after such a large bounty.
Flavor: A Sea Hag has turned the once fresh canal into polluted, dangerous waters. By defeating the hag, your party will begin the process of clearing the waters, making the canal once again passable. This can bring great notoriety for your party and Captain Ellis.
Creature Encounters:
Sea Hag CR 2
Merrow (coastal creatures) CR 2
Nymph CR 3 (homebrew)
Oni (minion of hag) CR 7
Loot:
Hag lair loot ideas here and here, including:
- An active Mirror of Life Trapping.
- A strange jar of coloured jelly. Upon closer inspection, you find it is a tiny-sized ooze in a jar.
- A cursed gold chain necklace. Once put on it cannot be removed. When the wearer speaks a lie a link is magically removed from the chain, the link clatters loudly to the ground. Lie enough and it begins to choke the wearer.
- A perfectly smooth, round stone the size of a human’s fist. If placed on the ground, it rolls 20 feet per round toward the nearest source of fresh water.
Oni Eyes (alchemy/herbalism)
Merrow Hide (Leatherwork)
Any Sunken Treasure
Bog
“Fantasy World Collab” by DesigningLua, CC License
Ideas for Environment: New creatures discovered, poisonous/healing/magical plants and fungi.
Adventure Hook: After taking extensive damage from a creature at sea, the ship is forced to find dry land for the boatswain to work. A reward from the gods, an uncharted island comes into view. Muggy, dark, and thick with decay, the land beyond the shores appear to be boggy. Excitedly, the doctor begins to clip strange-looking plants, exclaiming their medicinal import. If he can gather enough, he could create a salve to heal the decaying skin disease of a fellow passenger.
Creature Encounters:
Missing Link (homebrew, found in mud) CR 0
Black Fly (homebrew, diseased) CR 0
Shrieker (fungi) CR 0
Stirge (bat mosquito) CR ⅛
Bullywug (Monster Manual, Swamp) CR ¼
Violet Fungus CR ¼
Giant Slug (homebrew) CR ½
Shade Rat (homebrew, diseased) CR ½
Swarm of Leeches (homebrew) CR ½
Lizardfolk CR ½
Deadly Gecko (homebrew) CR 1
Dread Rat (homebrew, diseased) CR 1
Hulking Toad (homebrew) CR 2
Nightwing Bat (homebrew) CR 2
Noxious Toad (homebrew) CR 3
Night Hag CR 5
Shambling Mound (swamp) CR 5
Loot:
- Lizardfolk Hide (Leatherwork)
- Lizardfolk Heart of Semuanya (alchemy/herbalism)
- Bullywug Bladder (Leatherwork)
- Giant Toad Leg for arcane focus by Warlock
- Shambling Mound Root-Stem/Vines (alchemy/herbalism)
- Bat Pelt (Leatherwork)
Alchemist/Herbalist Supplies
- Gas Spore Malt
- Shrieker Malt
- Violet Fungus Malt
- Myconid Malt
- Sovereign Malt
Established Islands
“Shores of the Tarnak” by dominuself, CC License
Ideas for Environment: Inhabited, fun scanty towns, brawls, shops, taverns, intrigue among passengers
Adventure Hook: The cabin boy looks nervous as he walks the streets of this trading town, covering his face with his cloak. You all enter a tavern for well-earned rest. During your feast of turkey legs and ale, your eyes stop on a man unabashedly staring at your table, hand on the hilt of his scimitar. Does this have to do with the skittish cabin boy?
Adventure Hook 2: The local bard begins a jovial dancing tune on his flute. Warm ale convinces the crew that they’re confident enough to dance with the local crowd. The navigator, a bulky man with little grace, stumbles onto a table of gruff, unamused men. Drinks splash all over the meanest-looking one. He stands to confront the aghast navigator and pulls out a dagger.
Adventure Hook 3: The captain pays wages to the crew, which were more than expected thanks to the party’s hard work. The island is bustling with brightly-costumed folk, laughing as they rush toward the festivities. Colorful lamps line the street. Children dance around vibrant sparks of fireworks. There is much to see in town. An enigmatic set of dark, almond-shaped eyes lure the crewmembers walking with the party toward a dim, striped tent of the local oracle. What tales will she tell?
Creature Encounters:
Wererat (city) CR 2
Any NPC
Any creature
Uncharted Islands
“Risen 2 Dark Waters” by Nikulina-Helena, CC License
Ideas for Environment: Here are 100 ideas for unexplored islands. Island exploration could be a big part of your crew’s motivations. Perhaps a wealthy benefactor is paying good money for any adventuring crew to find an inhabitable island for him to claim, or the cartographer has been hired by royalty to expand the knowledge of their empire’s reach. Natives could be subject to rule they don’t know of. Groups of people could be marooned or shipwrecked on uncharted islands.
Creature Encounters:
Leech (homebrew) CR 0, wading through river or pool of water on island
Corpse Worm (homebrew, amphibious) CR 0
Black Fly (homebrew, diseased) CR 0
Giant Crab Variant (homebrew) CR ¼
Giant Leech (homebrew) CR ¼
Aarakocra (Monster Manual) CR ¼
Gnoll (uninhabited island) CR ½
Acid Bird (homebrew) CR ½
Greater Fire Ant (homebrew) CR 1
Giant Tortoise (homebrew) CR 2
Greater Flying Squirrel (homebrew) CR 2
Swarm of Trilobites (homebrew) CR 2, shallow ocean waters
Kapoacinth (stone gargoyles. 3.5e, may need modification) CR 4
Medusa Snake (homebrew) CR 6
Roc (bird) CR 11
Dragon Turtle CR 17
Loot:
Corpse Worm Hide (Leatherwork)
Roc Feathers (Leatherwork)
Snake Skin (Leatherwork)
Crab Claw (Weapon)
Gifts from Natives
New spices, medicinal plants, etc.
Coral Reef
“Deep Sea” by Deltamike, CC License
Ideas for Environment: Biodiversity in exploration, developed magically, difficult sailing, protects an island. Walk along the dead, shallow portions of the reef or dive deep to find living coral.
Adventure Hook: The crew is being paid to take the scientist to the coral reef to monitor its health, biome, and indigenous species. Your party must protect and chauffer the scientist.
Adventure Hook 2: An underwater resort has been built within a coral reef. The owners display their famed treasure, a giant pearl, discovered in depths below the coral reef. The captain hopes to learn more from the resort owners.
Creature Encounters:
Sea Urchin (homebrew) CR 0
Reef Shark CR ½
Coral Golem CR 6
Reef Reaver CR 7
Adult Coral Dragon CR 14
Coral Crawler CR 18
Loot:
Dragon Tail (alchemy/herbalism)
Dragon Hide (Leatherwork)
Dragon Claws, Scales, Horns, Skull (Smithing)
Amphibious Pet
Unexpected Winterous Region
“Terror” by Winerla, CC License
Ideas for Envirnoment: Floating Iceberg, large enough to be home to creatures and plants, treasure frozen inside, sea creature underwater is pushing it toward the ship to shipwreck. Wintery island. Eskimo Natives on island.
Adventure Hook: Northbound in search of a treasured item, the captain sails by a large iceberg. Glittering in the sun, you can see behind the exposed layers that have melted in the sun swords, skeletons, equipment, and treasure chests, just beyond the surface.
Adventure Hook 2: Northbound in search of a treasured item, the captain is leery while a passing iceberg. The mass of ice seems to follow the Aurora, picking up momentum as it moves along. A second iceberg appears from the side, forcing the captain to change course. As the fog dissipates, you see the ship sailing straight into a rocky cliffside!
Adventure Hook 3: The infamous Captain Broadbelt is fabled to have fled to the Northern islands with the entirety of his treasure after condemning his ship crew to death by Kraken. He went mad on a cold, dead island. Captain Ellis has decided to adventure in the North to find Broadbelt’s treasure.
Creature Encounters:
Giant Owl CR 1/4
Albino Penguin (homebrew) CR ½
Ice Mephit CR ½
Polar Bear CR 2
Saber Toothed Tiger CR 2
Winter Wolf CR 3
Yeti CR 3
Ice Troll (homebrew) CR 4
Mammoth CR 6
Frost Giant CR 8
Frostfell Warden CR 12
Icebreaker Shark CR 14
Malshanax (ruler of frozen planes of the abyss) CR 18
Loot:
Ice Giant Heart (alchemy/herbalism)
Troll Blood (alchemy/herbalism)
Owl Feathers (Calligraphy)
Yeti Hide/Throat (Leatherwork)
Mammoth Tusk (ivory, can be used to carve into statuette for Contingency Wizard spell)
Winter-themed spell scrolls from natives
Underwater Forest Biome
“Deep Dive” by Sayned, CC License
Ideas for Environment: Creatures live within, societies like sea elves inhabit, new plants, treasure hidden
Adventure Hook: Hundreds of feet below the Aurora, the party unexpectedly descends into a thick underwater forest. Pathways through the trees lead in various paths. Water critters peer at the travelers from their tree homes. The treasure your party is hoping to locate is somewhere in the forest, but navigating this may be difficult.
Creature Encounters:
Merfolk CR ⅛
Sea Elf CR 1/8
Kuo-toa (Monster Manual) CR ¼
Sahuagin CR ½
Dryad (modify for underwater) CR 1
Ixitxachitl (Out of the Abyss, intelligent manta rays) CR 2
Green Hag CR 3
Loot:
Jade Circlet (1,500 gp value, used in Druid/Wizard level 9 spell Shapechange)
Dryad heart (alchemy/herbalism)
Sahuagin Fin/Baron Heart (alchemy/herbalism)
Kuo-Toa Hide (Leatherwork)
Merfolk Hide (Leatherwork)
Hand of a Sahuagin Baron (Leatherwork)
Spell scrolls from sentient races like Merfolk
Shipwreck or Lost Treasure
“Forgotten Shipwreck” by xygyology, CC License
Ideas for Environment: Underwater Air Pocket, undead from wrecks, treasure that harms players, cursed treasure.
Shipwrecks and lost treasures will be the bulk of the adventure hooks for this campaign. Captain Ellis will sift through tales and have his navigators map radii of regions where the treasure could be.
Creature Encounters:
Lemure (fiend from banished soul) CR 0
Giant Hagfish (homebrew) CR ¼, Lives in corpse
Skeleton CR ¼
Shadow (shipwreck) CR ½
Animated Armor (treasure) CR 1
Harpy CR 1
Specter CR 1
Mimic CR 2
Rug of Smothering (treasure) CR 2
Wight (undead, shipwreck) CR 3
Ghost CR 4
Wraith CR 5
Xorn (near treasure) CR 5
Djinni (in treasure) CR 11
Planetar (treasure) CR 16
Loot:
Ghost/Shadow/Wraith vial of ectoplasm (alchemy/herbalism)
Harpy Feathers (Calligraphy)
Jewel-Encrusted Dagger (1,000 gp, component for Create Homunculus Wizard spell)
Oils and Unguents (1,000 gp, components for Druid Reincarnate spell)
Black Pearls (500 gp)
Silver bars
Gems
Pendants
Diamonds
Desert Island
“Desert Level” by PeterKmiecik, CC License
Ideas for Environment: This island could have once been tropical, or could have risen from the depths of the sea due to plate tectonic movements.
Adventure Hook: Once a prosperous island, this now barren wasteland is home of a nasty mean red dragon. His hoard of treasures has been sought by the greatest of adventuring parties, but none have prevailed. Captain Ellis has heard tales of an infamous artifact among the dragon’s treasures: The Devil’s Heart. With the Devil’s Heart powering the Aurora, the ship could travel speeds unheard-of by man. This is one item necessary to overcome Hangman’s Barrier, a series of dreadful currents that prevent further travel east outside of the kingdom.
Flavor: Your party could fight the dragon or try to deceive it, sneak past it, or bribe it. This encounter should be well into the adventure and after exploration has been nearly exhausted.
Creature Encounters:
Scorpion CR 0
Kobold CR ⅛
Flame Serpent CR 1
Minotaur CR 3
Cyclops CR 6
T-rex CR 8
Titan Scorpion (homebrew) CR 8
Marilith CR 16
Adult Red Dragon CR 17
Natives
Loot:
Cyclops eye (Abjuration, Alchemy, Herbalism)
Dragon Tail (alchemy/herbalism)
Dragon Hide (Leatherwork)
Dragon Claws, Scales, Horns, Skull (Smithing)
Minotaur Horns/Skeleton (alchemy/herbalism)
Minotaur Hide (Leatherwork)
Snake Skin (Leatherwork)
Treasure Chests
While Sailing
“The Ocean is Hungry” by Silberius, CC License
Ideas for Environment: Storms change ship paths, redirect to new islands, summoned by villain, damages ship, eye of storm contains special item or creature or person, can be overcome to bring crew together, rival ships battle
Creature Encounters:
Porpoise (homebrew) CR ¼
Sea Turtle (homebrew) CR ½
Pegasus CR 2
Air Elemental CR 5
Invisible Stalker (air, search for item) CR 6
Wyvern CR 6
Cloud Giant CR 9
Nalfeshnee (sky demons) CR 13
Storm Giant (amphibious) CR 13
Colossal Octopus (homebrew) CR 15
Kraken CR 23
Loot:
Cloud/Storm Giant Heart (alchemy/herbalism)
Kraken Eyes (alchemy/herbalism)
Pegasus Feather (Calligraphy)
Kraken Skull, Ribcage, Scales (Carpenter’s/Mason’s Tools)
Kraken Hide (Leatherwork)
Nalfeshnee Hide (Leatherwork)
Wyvern Wings (Leatherwork)
Supplies from rival ship
Commandeered ship
Deep Waters
“The Well of Eternity” by TomTC, CC License
This should be higher-level achievement; a reward for upgrading equipment. Deep sea pressure: upgrade equipment to search the same locations but at deeper elevation or new waters and caverns that are even deeper.
Creature Encounters:
Water Elemental CR 5
Aboleth CR 10
Loot:
Aboleth Mucous (alchemy/herbalism)
Aboleth Tail/Hide/Bladder (Leatherwork)
Lost Treasure
Magic weapons and items
Plants above and under the Water
“Fantasy Landscape” by Deevad, CC License
Poisonous, wondrous, medical, bioluminescent, sentient, home to species
See our downloadable Artificer’s Field Guide document for a list of plants and where to find them.
Creature Encounters:
General Exploration Underwater
“Underwater Environment” by H3Kate, CC License
Consider the following when creating encounters of groups of underwater creatures:
- Predators know how to stalk their prey. What team tactics would they use? Flanking? Cornering? Trickery?
- Is their eyesight underwater better than the players?
- The sea is their domain. They know how to hide. How can you realistically surprise the players without making them feel like the encounter was unfair?
Creature Encounters:
Sea Dog (homebrew) CR ¼, swim in packs
Giant Eel (homebrew) CR 2
Giant Octopus Variant (homebrew) CR 2
Chuul (crustaceans) CR 4
Colossal Octopus (homebrew) CR 15
Loot:
Chuul Carapace/Pincers (Smithing)
Underwater Temple
“Underwater Kingdom” by Silberius, CC License
Adventure Hook: Angering the gods, ancient civilizations sank. Whole cities were destroyed. Only temples, protected by the magic of their priests, managed to survive. But eventually they, too, flooded. Priceless artifacts and treasures have been left untouched for millennia. Now is the time to search for them.
Creature Encounters:
Couatl CR 4
Medusa CR 6
Young Copper Dragon (homebrew) CR 7
Gynosphinx (temple) CR 11
Androsphinx (temple) CR 17
Scylla (Greek myth) CR 18
Lich CR 21
Loot:
Dragon Tail (alchemy/herbalism)
Dragon Hide (Leatherwork)
Dragon Claws, Scales, Horns, Skull (Smithing)
Couatl Hide (Leatherwork)
Reliquary containing a Sacred Relic (1,000 gp. Component for Holy Aura spell)
Jeweled Horn (100 gp, Component for Clairvoyance spell)
Ancient and possibly cursed treasure
Cave
“The Eldergleam” by Solace-Grace, CC License
Adventure Hook: The cartographer purchases an antique map at a seasoned island village. Symbols are drawn to indicate a port where one may now find a rocky precipice. Island history explains that tectonic movement shifted the island upward, creating a mountainous side. Your party dives alongside the rocky barrier. One-hundred feet down, they spot a crevice large enough for a creature. Upon entering, they discover a ginormous air-filled cave, littered with strewn rotten planks, moldy rope, petrified crates. Your party may have found an old port of ineffable value.
Creature Encounters:
Dust Mephit (cave) CR ½
Deep Gnome (cave to underdark) CR ½
Rust Monster (cave) CR ½
Ankheg (insect underground) CR 2
Basilisk CR 3
Crag Spider (homebrew) CR 3
Sword Spider (homebrew) CR 8
Behir (cave) CR 11
Loot:
Basilisk Stomach (alchemy/herbalism)
Spider Legs (alchemy/herbalism)
Behir Hide/Tail (Leatherwork)
Deep Gnome Hide (Leatherwork)
Gemstones
Magic weapons from past adventurers
Treasure Examples
Give treasure at your discretion.
Remember that these people are simply employees working a job and will not receive even a fraction of the treasure they discover unless their greed overcomes their judgement.
“Mermaid Grotto” by SeaOfFireflies, CC License
To rule out the possibility of confounding your campaign goals, allow rewards to be received in different ways: maybe the Captain allows them to keep one artifact from each dive, items they find in addition to the specific item he seeks, or perhaps the Captain creates a store of items that they can use. You could give them boons for noble deeds, rewards from sentient species they help, or items they can purchase on populated islands.
- Chest of silver 50 gp Total
- Chest of gold 250 gp Total
- Small chest filled with gems 250 gp Total
- Small box of pearls 250 gp Total
- 4x Small gold bracelet 100 gp Total
- Pair of engraved bone dice 25 gp ea.
- Carved bone statuette of mermaid 50 gp ea.
- Spyglass 100 gp
- Compass 100 gp
- Silver comb with Moonstones valued at 900 gp.
- Silver Ewer valued at 40 gp.
- Violet Garnet valued at 400 gp.
- Chrysoberyl valued at 40 gp.
- Tomb Jade valued at 400 gp.
- Thunderstones valued at 30 gp.
- Hyaline valued at 16 gp.
- Jade valued at 160 gp.
- Golden circlet with four Aquamarines valued at 1,000 gp.
List of Items by Category
List of 100 Aquatic Items
Cursed treasure
Here is a great list of 100 artifacts of great power the Captain could be after.
Underwater Combat Rules
Typical combat underwater may not be very feasible. For instance, armor is too heavy to wear in water, ranged weapons fail, and fire damage is at a huge disadvantage. But underwater combat is a new ballpark for your players to explore.
Consider the rules from the Player’s Handbook:
“When making a melee weapon attack, a creature that doesn’t have a swimming speed (either natural or granted by magic) has disadvantage on the attack roll unless the weapon is a dagger, javelin, shortsword, spear, or trident.
A ranged weapon attack automatically misses a target beyond the weapon’s normal range. Even against a target within normal range, the attack roll has disadvantage unless the weapon is a crossbow, a net, or a weapon that is thrown like a javelin (including a spear, trident, or dart).”
And from the DM’s Guide:
“Unless aided by magic, a character can’t swim for a full 8 hours per day. After each hour of swimming, a character must succeed on a DC 10 Constitution saving throw or gain one level of exhaustion.
A creature that has a swimming speed-including a character with a ring of swimming or similar magic can swim all day without penalty and uses the normal forced march rules in the Player’s Handbook.
Swimming through deep water is similar to traveling at high altitudes, because of the water’s pressure and cold temperature. For a creature without a swimming speed, each hour spent swimming at a depth greater than 100 feet counts as 2 hours for the purpose of determining exhaustion. Swimming for an hour at a depth greater than 200 feet counts as 4 hours.
Underwater Visibility
Visibility underwater depends on water clarity and the available light. Unless the characters have light sources, use the Underwater Encounter Distance table to determine the distance at which characters underwater become aware of a possible encounter.“
Consider the following questions:
- How can my players cast verbal component spells underwater?
- How do my players store their weapons while exploring?
- Can my players have a line of sight to cast spells?
Underwater Armor
Armor specific for underwater endeavors should not be easy to come by. Players should look for ways to improve their armor or be rewarded throughout the game with upgrades based on performance.
Decide beforehand where your players may run into unique types of armor, such as in a Sea Dwarf city or using the hide of a sea monster.
Examples of Armor a Player Can Swim in (PHB & Homebrew)
| Armor Type | AC | Effects | Description | Price |
|---|---|---|---|---|
| Padded Light | 11 + Dex | Disadvantage on Stealth Underwater | Standard PHB | 5 gp |
| Leather Light | 11 + Dex | Disadvantage on Stealth Underwater | Standard PHB | 10 gp |
| Studded Leather Light | 12 + Dex | Disadvantage on Stealth Underwater, -5 Swim Speed | Standard PHB | 45 gp |
| Electric Eel Hide | 12 + Dex | Opponents that hit the wearer with unarmed attacks or weapons composed mostly of metal take 1d6 points of lightning damage | Black and slimy looking | 1,000 gp |
| Crab Chitin | 14 + Dex | — | Thick, coarse, and buoyant | 1,000 gp |
| Hydra Leather Armor | 14 + Dex | Resistance to poison and acid damage | Smooth green scale mail | 1,500 gp |
| Pearlsteel Half Plate | 15 + Dex | -5 Swim Speed | Gleaming, shining steel covered with a blue-white sheen like mother of pearl | 2,250 gp |
| Coral Splint Armor | 17 | Disadvantage to Stealth | Narrow vertical strips of reddish coral riveted to a backing of leather | 5,000 gp |
Underwater Weapons
| Weapon | Damage | Effects | Description | Cost |
|---|---|---|---|---|
| Krakentooth Trident | 1d6 piercing | Once per short rest, the Krakentooth can omit one lightning bolt that deals 8d6 (Dexterity saving throw success = half damage) in a 5’ x 100’ line. | Nearly 7 feet in length, the head of this trident reflects a Kraken, with its head at the base of the prongs and tentacles forming the three prongs. | 25,000 gp |
| Crab Claw Hammer | 1d8 bludgeoning | — | This hammer consists of the top half of a crab’s claw, fastened to a hilt. Its ergonomic shape allows it to be swung underwater with ease. | 50 gp |
| Sea Glass weapon | Depends on weapon type. See Weapons Equipment table in PHB. | Can be enchanted. | Lighter and therefore easier to maneuver in water, weapons of this type are perfect for underwater combat can be enchanted. | 2,000 – 20,000 gp |
| Shark Tooth Spear | 1d6 piercing | On a critical hit, the target receives a lingering wound. | Shark Tooth Spears are strong and durable, yet light enough to be easily maneuvered under water. | 101 – 500 gp |
Subplot
The Aurora is partially funded by the crown. Captain Ellis’ successful adventuring has reached the ears of all in the realm. When political unrest rattles the kingdom, Captain Ellis is asked to harbor the queen to a neighboring kingdom. Your party is acknowledged as some of the best adventurers in the land and can safely protect her.
Additional Resources:
This 3.5 edition manual Stormwrack provides extensive research on sea adventures: aquatic terrains, additional seafaring races and classes, items, weapons, navigation and naval combat, and more. Note that you will have to modify official material to fit the 5th Edition criteria that you’ll be playing with.
You can find a set of house rules for ship combat from the OldDungeonMaster’s blog.
The SaveOrDie podcast released neat information about playing an underwater adventure, including visibility, movement, pressure and depth, and weapons.
Here is a list of aquatic monster and hero races from Tribality, and here are all of their nautical-themed articles.
See this magnificent anthology of Monster Ecology, compiled by reddit user u/Merchent100:
Wow! That was comprehensive!
Added to the Blog Database.