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Movement: Swim
301 creatures
| Name ▲ | CR | Type | Alignment | Size | Environment | Description |
|---|---|---|---|---|---|---|
| Abaia | 10 | magical beast | N | Huge | warm lakes | This multi-eyed eel’s brightly colored markings shift in complex, ever-changing patterns. |
| Aboleth | 7 | aberration | LE | Huge | any aquatic | |
| Adaro | 3 | monstrous humanoid | NE | Medium | warm oceans | This hybrid of human and shark holds its spear menacingly, thick, glistening saliva dripping... |
| Adult Black Dragon | 11 | dragon | CE | Large | ||
| Adult Brine Dragon | 11 | dragon | LN | Large | ||
| Adult Bronze Dragon | 13 | dragon | LG | Huge | ||
| Adult Cloud Dragon | 13 | dragon | N | Huge | ||
| Adult Gold Dragon | 15 | dragon | LG | Huge | ||
| Adult Green Dragon | 12 | dragon | LE | Huge | ||
| Adult Sea Dragon | 12 | dragon | CG | Huge | ||
| Adult White Dragon | 10 | dragon | CE | Large | ||
| Aghasura | 11 | outsider | LE | Huge | any (Hell) | |
| Ahuizotl | 6 | magical beast | NE | Large | warm lakes, rivers, or swamps | This bear-sized beast has a body like a squat simian, a dog’s face, and a long tail that ends in... |
| Akhlut | 13 | magical beast | N | Huge | cold lakes, plains, or oceans | A dorsal fin rises up from the back of this immense black-and- white-furred, wolflike beast. |
| Alpluachra | 1/2 | fey | CN | Diminutive | temperate forests or fresh water | This minuscule creature resembles a newt with three tails. It’s covered in a transparent slime,... |
| Amoeba, Giant | 1 | ooze | N | Small | any land or underground | This blob of protoplasm is somewhat transparent, allowing the bones of undigested meals and a... |
| Amoeba Swarm | 1 | ooze | N | Fine | any land or underground | Thousands of tiny gelatinous clots of animate ooze swarm in a wet mound, surrounded by a cloying... |
| Amphisbaena | 4 | magical beast | N | Large | temperate hills or underground | This large snake has two heads, one at each end of its long, coiling body. Both display large... |
| Ancient Black Dragon | 16 | dragon | CE | Huge | warm deserts | |
| Ancient Brine Dragon | 16 | dragon | LN | Huge | any sky (Plane of Air) | |
| Ancient Cloud Dragon | 18 | dragon | N | Gargantuan | any underground (Plane of Earth) | |
| Ancient Gold Dragon | 20 | dragon | LG | Gargantuan | temperate mountains | |
| Ancient Green Dragon | 17 | dragon | LE | Gargantuan | warm mountains | |
| Ancient Sea Dragon | 17 | dragon | CG | Gargantuan | temperate or warm mountains | |
| Ancient White Dragon | 15 | dragon | CE | Huge | warm deserts | |
| Apkallu | 23 | outsider | LN | Large | any (lawful planes) | This muscular humanoid possesses a hawk’s head and large, bird- like wings. It is dressed in... |
| Archelon | 5 | animal | N | Huge | warm or temperate water or coastlines | |
| Asurendra | 20 | outsider | LE | Huge | any (Hell) | |
| Bagiennik | 6 | fey | CN | Small | cold rivers | This small, lizardlike creature has a humanoid upper body and a long tail with frilled extensions. |
| Bakekujira | 17 | undead | NE | Colossal | any oceans | This hulking mass of blubber and bone looks like it was once a whale. Ghostly flames glow in... |
| Basilosaurus | 12 | animal | N | Gargantuan | any oceans | |
| Blindheim | 2 | magical beast | N | Small | any underground | The size of a short, stocky humanoid with webbed feet and claws, this frog-like creature has... |
| Blue Whale | 12 | animal | N | Colossal | any oceans | |
| Boggard | 2 | humanoid | CE | Medium | temperate marshes | |
| Boilborn | 1 | ooze | N | Tiny | any | Like some taut pustule ready to burst, this mobile wound scuttles on a bristle of slick hairs. |
| Bokrug | 27 | magical beast | CN | Large | any water | |
| Bone Ship | 18 | undead | CE | Colossal | any oceans | Muscle holds together the large bones that form the hull of this ship. Rotting sails hang from... |
| Bull Shark | 2 | animal | N | Medium | any oceans | |
| Bunyip | 3 | magical beast | N | Medium | any aquatic | A disturbing combination of shark and seal, this brown-furred creature has a wide mouth filled... |
| Cameroceras | 11 | animal | N | Huge | any oceans | Emerging from the open end of a long, conical shell, this huge creature’s unblinking eyes peer... |
| Carnivorous Blob | 13 | ooze | N | Colossal | any | Rolling and twitching like a massive wad of translucent ooze, this crimson blob reaches out... |
| Catoblepas | 12 | magical beast | N | Large | any swamps | This ugly creature has a boar-like head with short antlers, a thick bullish body covered in... |
| Cecaelia | 5 | monstrous humanoid | CN | Medium | warm water | In place of legs, this handsome humanoid sports an octopus’s eight writhing tentacles. |
| Ceratioidi | 3 | monstrous humanoid | N | Medium | any saltwater | This flabby, fishlike humanoid has the wide mouth, bulging eyes, and dangling, luminescent flesh... |
| Cetaceal | 15 | outsider | NG | Medium | any water (Nirvana) | |
| Cetus | 13 | dragon | CN | Colossal | any oceans | This enormous scaled serpent has the head of a shark, powerful claws, and a maw wide enough to... |
| Charda | 7 | monstrous humanoid | CN | Small | cold aquatic or underground | Armored in dense, bony plates, this four-armed creature drools wretched strings of black bile... |
| Charybdis | 13 | aberration | CN | Gargantuan | any oceans | An immense spiny monster, its back plated in chitin and its belly in thick folds of blubber,... |
| Cherufe | 13 | magical beast | NE | Huge | any mountains | This towering reptilian humanoid seems to be made of obsidian scales over a molten magma core. |
| Chuul | 7 | aberration | CE | Large | temperate swamps | |
| Clockwork Dragon | 16 | construct | N | Huge | any land | Though made of thousands of metal parts, this masterpiece of gleaming metal glides through the... |
| Clockwork Leviathan | 12 | construct | N | Huge | any | Long and metallic, this serpentine construction resembles a mechanical eel with several... |
| Compsognathus | 1/2 | animal | N | Tiny | temperate or warm forests or plains | |
| Constrictor Snake | 2 | animal | N | Medium | warm forests, swamps, and fresh water | |
| Crab Swarm | 4 | vermin | N | Diminutive | any aquatic | |
| Crag Linnorm | 14 | dragon | CE | Gargantuan | cold hills | |
| Crocodile | 2 | animal | N | Large | warm rivers and marshes | |
| Cthulhu | 30 | aberration | CE | Colossal | any (R’lyeh) | |
| Cuero | 5 | aberration | N | Large | temperate lakes or rivers | The pink, fleshy underside of this flat, aquatic creature features a large circular maw of fangs. |
| Dagon | 28 | outsider | CE | Huge | any oceans (Abyss) | |
| Death’s Head Jellyfish | 1 | vermin | N | Small | any oceans | |
| Deep Merfolk | 3 | humanoid | N | Medium | any oceans (trenches) | |
| Deep One | 1 | monstrous humanoid | CE | Medium | any water | This lumbering creature’s gray-green hide glistens with moisture, and saliva dribbles from its... |
| Deep One Hybrid | 1/2 | humanoid | CE | Medium | any urban | This elderly man’s wide-mouthed, staring countenance and webbed hands suggest a sinister taint... |
| Deep Sea Serpent | 19 | magical beast | N | Gargantuan | any oceans | |
| Devilfish | 4 | magical beast | NE | Large | any aquatic | This purple, seven-armed octopoid monstrosity is the size of a horse, with hook-lined tentacles... |
| Dire Crocodile | 9 | animal | N | Gargantuan | warm rivers and marshes | |
| Dire Polar Bear | 8 | animal | N | Large | cold coastlines or plains | |
| Dire Rat | 1/3 | animal | N | Small | any urban | |
| Dire Shark (Megalodon) | 9 | animal | N | Gargantuan | any ocean | |
| Divine Guardian Hydra | 5 | magical beast | N | Huge | temperate ruins | |
| Dolphin | 1/2 | animal | N | Medium | any ocean | |
| Dragon Turtle | 9 | dragon | N | Huge | temperate aquatic | |
| Drakainia | 25 | aberration | NE | Huge | any | This woman’s upper body is shapely and beautiful, but her lower body is bloated, with pulsating... |
| Draugr | 2 | undead | CE | Medium | any coastal | This barnacle-encrusted walking corpse looks like a zombie, but is dripping with water and gives... |
| Drowning Devil (Sarglagon) | 8 | outsider | LE | Large | any (Hell) | |
| Echeneis | 1 | magical beast | N | Small | warm or temperate water | This thin, colorful fish has a broad, segmented sucker above its narrow mouth. A line of spines... |
| Elasmosaurus | 7 | animal | N | Huge | warm aquatic | |
| Elder Deep One | 14 | monstrous humanoid | CE | Gargantuan | any water | |
| Elder Fire Elemental | 11 | outsider | N | Huge | any (Plane of Water) | |
| Elder Ice Elemental | 11 | outsider | N | Huge | any (Plane of Air) | |
| Elder Mud Elemental | 11 | outsider | N | Huge | ||
| Elder Thing | 5 | aberration | LN | Medium | any | This strange being has a star-shaped head and numerous writhing appendages arranged radially... |
| Elder Water Elemental | 11 | outsider | N | Huge | ||
| Electric Eel | 2 | animal | N | Small | warm fresh water | |
| Elohim | 23 | outsider | N | Huge | any (extraplanar) | This one-eyed being is a strange mix of insects, fungi, and other living things shaped into a... |
| Emperor Cobra | 5 | animal | N | Large | temperate or warm swamps | |
| Emperor Walrus | 8 | animal | N | Gargantuan | cold oceans | |
| Encantado | 8 | fey | CN | Medium | warm rivers | This graceful creature combines the features of a human and a river dolphin. |
| Faerie Dragon | 2 | dragon | CG | Tiny | temperate and warm forest | A pair of brightly colored butterfly wings sprouts from the back of this miniature dragon. A... |
| Fey Giant Toad | 3 | fey | CN | Large | temperate forests, plains, or swamps | |
| Fjord Linnorm | 16 | dragon | CE | Gargantuan | cold mountainous coastlines | |
| Forest Drake | 4 | dragon | LE | Large | any forests | |
| Fossegrim | 4 | fey | NE | Medium | cold or temperate water (waterfalls) | This striking, blue-eyed man with luminous skin and flowing white hair holds an ethereal harp. |
| Freezing Flow | 4 | ooze | N | Large | any cold | This transparent blue formation of ice is as forbidding as the serpent it resembles. |
| Frog Father | 5 | animal | N | Huge | warm marshes or water | This elephantine amphibian has a grotesquely long tongue and beady eyes. |
| Froghemoth | 13 | aberration | N | Huge | temperate marsh | |
| Fuath | 1 | fey | CE | Tiny | any water | |
| Fungal Nymph | 8 | plant | CG | Medium | any ruins or underground | |
| Galvo | 9 | magical beast | NE | Medium | any water | This creature is composed of dozens of electric eels tightly knotted into a slithering, humanoid... |
| Gar | 1 | animal | N | Medium | temperate freshwater | This long, lean fish has a muscular body and a head with long jaws filled with sharp teeth. |
| Ghawwas | 10 | outsider | NE | Large | any (Abaddon) | |
| Giant Anaconda | 10 | animal | N | Gargantuan | warm swamps | |
| Giant Crab | 2 | vermin | N | Medium | any aquatic | |
| Giant Dragonfly Nymph | 3 | vermin | N | Small | temperate or warm water | |
| Giant Frog | 1 | animal | N | Medium | temperate or warm marshes and aquatic | |
| Giant Gar | 6 | animal | N | Huge | temperate freshwater | |
| Giant Jellyfish | 7 | vermin | N | Large | any oceans | |
| Giant Leech | 2 | vermin | N | Medium | temperate or warm marshes | |
| Giant Mantis Shrimp | 9 | vermin | N | Medium | warm coastlines | |
| Giant Muckdweller | 2 | magical beast | N | Large | temperate marshes | |
| Giant Octopus | 8 | animal | N | Large | any ocean | |
| Giant Seahorse | 3 | animal | N | Large | any oceans | |
| Giant Snapping Turtle | 9 | animal | N | Gargantuan | temperate or warm water or shore | |
| Giant Squid | 9 | animal | N | Huge | any ocean | |
| Giant Toad | 2 | animal | N | Large | temperate forests, plains, or swamps | |
| Gibbering Mouther | 5 | aberration | N | Medium | any underground | |
| Globster | 5 | ooze | N | Large | any oceans or coastlines | This grotesque mass of blubber and rancid flesh piles up hideously upon itself, opening a vast... |
| Goblin Snake | 1 | aberration | CE | Small | any underground or swamps | A gray, lipless goblin head with serpent’s fangs sits atop the sinuous black body of this... |
| Goliath Frog | 3 | animal | N | Large | ||
| Gorynych | 15 | dragon | CE | Huge | temperate forests | This sleek, three-headed dragon rears up on its hind legs, wings spread and flames licking out... |
| Greater Ice Elemental | 9 | outsider | N | Huge | ||
| Greater Mud Elemental | 9 | outsider | N | Huge | ||
| Greater Water Elemental | 9 | outsider | N | Huge | ||
| Great White Shark | 4 | animal | N | Huge | any oceans | |
| Great White Whale | 14 | animal | N | Colossal | any oceans | |
| Green Hag | 5 | monstrous humanoid | CE | Medium | temperate marshes | |
| Grindylow | 1/2 | aberration | CE | Small | any water | With a large head and numerous teeth, this unsightly creature resembles a goblin from the waist... |
| Grodair | 5 | magical beast | CN | Medium | any water or coastlines | Several water-dripping tentacles sprout from this four-eyed fish’s belly, while long fins... |
| Grootslang | 16 | magical beast | CE | Gargantuan | warm lakes and rivers | This enormous beast has the combined features of an elephant and a serpent. Its tremendous maw... |
| Guardian Dragon | 24 | dragon | N | Gargantuan | any | This immense dragon coils its long, serpentine body beneath spreading wings, its eyes glittering... |
| Haniver | 1/2 | fey | N | Tiny | temperate coasts | |
| Heikegani | 4 | aberration | NE | Small | any coastlines | The carapace of this large crab resembles a scowling face, its eyes seething with an ancient fury. |
| Hezrou | 11 | outsider | CE | Large | any swamp (Abyss) | |
| Hippocampus | 1 | magical beast | N | Large | any water | This creature has the foreparts of a horse and the hindquarters of a fish. Its forelegs end in... |
| Huge Ice Elemental | 7 | outsider | N | Huge | ||
| Huge Mud Elemental | 7 | outsider | N | Huge | ||
| Huge Water Elemental | 7 | outsider | N | Huge | ||
| Hungry Flesh | 3 | ooze | N | Large | any land or underground | A quivering pile of tumorous flesh, this creature leaves a trail of slime as it hungrily... |
| Hydra | 4 | magical beast | N | Huge | temperate marshes | |
| Hydrodaemon | 8 | outsider | NE | Large | any (Abaddon) | |
| Ice Linnorm | 17 | dragon | CE | Colossal | cold hills and mountains | |
| Ichthyocentaur | 5 | monstrous humanoid | N | Large | temperate oceans or coastlines | This creature has an athletic human torso from the waist up, but its lower body consists of two... |
| Iku-Turso | 8 | aberration | NE | Medium | cold or temperate water or underground | This grotesque, emerald-scaled creature resembles a crossbreed of an eel, a viperfish, and a... |
| Imentesh | 10 | outsider | CN | Large | any (Limbo) | |
| Incutilis | 2 | aberration | LE | Tiny | any oceans | This strange nautilus drags itself forward on oversized tentacles, its crimson-streaked flesh... |
| Isonade | 15 | magical beast | CE | Gargantuan | any oceans | This massive horror looks like a shark protected by a crab carapace, with a tail, flanks, and... |
| Jellyfish Swarm | 6 | vermin | N | Diminutive | any aquatic | All but invisible in the water, this foul swarm of fist-sized jellyfish wriggles and writhes, a... |
| Jorogumo | 12 | monstrous humanoid | NE | Medium | temperate mountain valleys | Eight spindly spider legs, flocked with coarse black hairs, stretch from the back of this... |
| Julunggali | 21 | magical beast | N | Colossal | any land or water | Resplendent lilac and white scales adorn this gigantic serpent. A number of sharp, short horns... |
| Kappa | 2 | monstrous humanoid | CN | Small | any lake or river | This humanoid turtle crouches near the water, a suspicious look in its eyes. The top of its... |
| Karkinoi | 6 | monstrous humanoid | CE | Large | any water | This hulking mix of ogre and crab has one huge pincer that snaps menacingly, while its other arm... |
| Kawa Akago | 3 | plant | N | Small | temperate marshes or rivers | This combination of a lily pad and a flytrap is ringed with horrifying fangs and has another... |
| Keketar | 17 | outsider | CN | Large | any (Limbo) | |
| Kelpie | 4 | fey | NE | Medium | any water | This hideous humanoid creature has slimy, transparent skin; webbed, humanoid hands; and a... |
| Ketesthius | 13 | magical beast | LE | Gargantuan | any oceans or coastlines | This enormous wolf-headed sea serpent’s maw leads into what seems to be an endless expanse within. |
| Killer Seahorse | 5 | animal | N | Huge | any oceans | |
| Kraken | 18 | magical beast | NE | Gargantuan | any ocean | |
| Lamia Matriarch | 8 | monstrous humanoid | CE | Large | any land | This creature looks like a beautiful human woman from the waist up, but below is the body and... |
| Large Ice Elemental | 5 | outsider | N | Large | ||
| Large Mud Elemental | 5 | outsider | N | Large | ||
| Large Water Elemental | 5 | outsider | N | Large | ||
| Leech Swarm | 4 | vermin | N | Diminutive | temperate or warm marshes | |
| Lizardfolk | 1 | humanoid | N | Medium | temperate swamps | |
| Locathah | 1/2 | humanoid | N | Medium | temperate or warm aquatic | This lean humanoid bears crested fins on its head and back, and has the wide-eyed and... |
| Lorelei | 12 | aberration | NE | Large | any coastlines | This strange creature appears to be a gigantic human head carved from stone, with thick... |
| Lukwata | 11 | magical beast | N | Huge | warm rivers, lakes, and swamps | A long, spiny fin runs down the length of the dolphinlike body of this eel-headed predator. |
| Lusca | 17 | magical beast | CE | Gargantuan | warm oceans | This beast has three sharklike heads on short, scaly necks, while its lower body appears to be... |
| Makara Vahana | 9 | magical beast | N | Huge | any | |
| Manta Ray | 1 | animal | N | Large | warm oceans | |
| Marid | 9 | outsider | CN | Large | any (Plane of Water) | |
| Marsh Giant | 8 | humanoid | CE | Large | temperate marshes | |
| Medium Ice Elemental | 3 | outsider | N | Medium | ||
| Medium Mud Elemental | 3 | outsider | N | Medium | ||
| Medium Water Elemental | 3 | outsider | N | Medium | ||
| Megalania | 7 | animal | N | Huge | warm forests or plains | |
| Merfolk | 1/3 | humanoid | N | Medium | temperate ocean | |
| Merrow, Freshwater | 3 | humanoid | NE | Large | temperate lakes or rivers | |
| Merrow, Saltwater | 6 | humanoid | NE | Huge | temperate oceans | |
| Mobogo | 10 | magical beast | CE | Huge | temperate swamps | This grotesque creature looks like a gigantic toad with leathery wings, fangs, horns, and three... |
| Mogaru | 28 | magical beast | CN | Colossal | warm forests or water | |
| Monitor Lizard | 2 | animal | N | Medium | warm forests or plains | |
| Muckdweller | 1/4 | magical beast | N | Small | temperate marshes | This bipedal lizard has mottled gray-and-brown flesh. A short dorsal fin runs the length of its... |
| Mudlord | 6 | outsider | N | Medium | temperate or warm marshes or underground | This fluid creature’s roughly humanoid form is composed entirely of thick gobbets of soggy, brown mud. |
| Narwhal | 3 | animal | N | Large | cold oceans | |
| Naunet | 7 | outsider | CN | Large | any (Limbo) | |
| Nereid | 10 | fey | CN | Medium | any aquatic | This beautiful woman has pearlescent skin and long, dark hair. Her nudity is barely hidden by a... |
| Nightwave | 20 | undead | CE | Colossal | any (Negative Energy Plane) | |
| Ningen | 16 | monstrous humanoid | N | Colossal | cold oceans | This enormous flippered creature is as pale as an iceberg and is nearly as large. |
| Ningyo | 1 | monstrous humanoid | NE | Small | warm oceans | This dog-sized creature combines the upper half of a deformed monkey with the lower half of a... |
| Nixie | 1 | fey | N | Small | temperate aquatic | As it gracefully swims through the water, it becomes clear that this small, green-skinned... |
| Nuckelavee | 9 | fey | NE | Large | cold swamps or coastlines | This skinless creature resembles a horse and its humanoid rider, fused into a single hideous... |
| Nycar | 2 | dragon | CN | Tiny | cold marshes | This cruel-looking serpent is about the size of a housecat, with two forearms and... |
| Nymph | 7 | fey | CG | Medium | temperate forest | |
| Ocean Giant | 14 | humanoid | CG or CE | Huge | any oceans | |
| Oceanid | 7 | fey | CN | Medium | any oceans | This beautiful woman is clad only in sea foam and her long, white hair, which cascades over her body. |
| Octopus | 1 | animal | N | Small | temperate or cold ocean | |
| Omox | 12 | outsider | CE | Medium | any (the Abyss) | |
| Ophiotaurus | 17 | magical beast | N | Gargantuan | warm hills, plains, or swamps | This enormous russet serpent has the head and forequarters of a ruddy bull with bronze horns and hooves. |
| Orca | 5 | animal | N | Huge | cold oceans | |
| Otter | 1/4 | animal | N | Tiny | any water | |
| Pazuzu | 30 | outsider | CE | Large | any (Hell) | |
| Peluda | 10 | dragon | NE | Large | temperate marshes or plains | This long-necked dragon has steamy breath, a lashing tail, and a back covered in hundreds of quills. |
| Penguin | 1/3 | animal | N | Small | cold oceans | |
| Piscodaemon | 10 | outsider | NE | Medium | any (Abaddon) | |
| Plankta | 17 | aberration | NE | Colossal | any oceans | The shattered remnants of buildings and statues can be seen in this shuddering mass of wet, rugged rock. |
| Platypus | 1/6 | animal | N | Tiny | temperate or warm rivers | |
| Plesiosaurus | 2 | animal | N | Large | temperate or warm swamps or water | |
| Poison Frog | 1/2 | animal | N | Tiny | warm marshes and aquatic | |
| Polar Bear | 5 | animal | N | Large | cold coastlines or plains | |
| Purple Worm | 12 | magical beast | N | Gargantuan | any underground | |
| Putrid Ooze | 11 | ooze | N | Huge | any | Masses of carrion and debris break the inky surface of this enormous, undulating sludge. |
| Qallupilluk | 7 | monstrous humanoid | LE | Medium | cold oceans | This hag’s lumpy hide, tangled black hair, and ragged garments drip with icy water, though she... |
| Raktavarna | 2 | outsider | LE | Tiny | any | |
| Rat | 1/4 | animal | N | Tiny | any temperate | |
| Rat King | 5 | magical beast | N | Small | any urban or underground | Squeaks and chittering cries rise from a tangle of diseased rats with their tails knotted together. |
| Ratling | 2 | magical beast | CE | Tiny | any urban | This ratlike creature has tiny human hands in place of its front paws, and an unnerving human... |
| Rat Plague Swarm | 11 | magical beast | LE | Tiny | ||
| Rat Swarm | 2 | animal | N | Tiny | any | |
| Reefclaw | 1 | aberration | CN | Small | any water (coastal) | Blood-red spines run the length of this frightening creature, which resembles a lobster in the... |
| Riftcreeper | 15 | ooze | CE | Gargantuan | any mountains (Abyss) | This slithering mass of bubbling red ooze extrudes a nest of long, thin tendrils, as if tasting... |
| River Drake | 3 | dragon | NE | Medium | temperate rivers or lakes | |
| Rusalka | 12 | fey | NE | Medium | any water | This beguiling female figure is partly obscured by long flowing hair that dances and flows... |
| Sahuagin | 2 | monstrous humanoid | LE | Medium | temperate or warm ocean | |
| Sapphire Jellyfish | 11 | vermin | N | Huge | warm or temperate oceans | |
| Sargassum Fiend | 9 | plant | N | Large | any oceans | This shifting mass of green seaweed transforms from the shape of a humanoid back to a patch of... |
| Scylla | 16 | aberration | CE | Huge | any water | This horrifying creature has the upper body of a beautiful woman, but a lower body of snapping... |
| Sea Bonze | 15 | undead | NE | Gargantuan | any oceans | Massive and blacker than the darkest depths of the sea, this colossal watery form glares with... |
| Sea Cat | 4 | magical beast | N | Large | warm coastlines | This fierce creature merges the front half of a great cat with the tail and other... |
| Sea Drake | 6 | dragon | NE | Large | any coastlines | |
| Sea Hag | 4 | monstrous humanoid | CE | Medium | any aquatic | |
| Seal | 1/3 | animal | N | Small | any oceans | |
| Sea Serpent | 12 | magical beast | N | Gargantuan | any ocean | |
| Seaweed Leshy | 3 | plant | N | Small | any ocean or coastline | |
| Seaweed Siren | 13 | magical beast | CN | Large | any coastlines | This creature’s three singing heads sway atop serpentine necks that extend from a bulbous body... |
| Selkie | 5 | monstrous humanoid | CN | Medium | cold oceans | This sleek, aquatic creature has short gray fur, webbed hands ending in sharp claws, and a mouth... |
| Shambling Mound | 6 | plant | N | Large | temperate forest or marshes | |
| Shark | 2 | animal | N | Large | any ocean | |
| Shark-Eating Crab | 7 | vermin | N | Huge | any water | |
| Shen | 24 | dragon | N | Gargantuan | any water | This serpentine dragon with gold scales constantly contorts into a pattern of rings and knots. |
| Shipwrecker Crab | 13 | vermin | N | Colossal | any water | |
| Shocker Lizard | 2 | magical beast | N | Small | warm marshes | |
| Shoggoth | 19 | ooze | CN | Huge | cold aquatic or underground | |
| Siyokoy | 10 | aberration | N | Medium | any ocean | This eel-like creature sports sharp frills that run along the back of humanoid torso and down... |
| Skum (Ulat-Kini) | 2 | monstrous humanoid | LE | Medium | temperate or cold aquatic or underground | |
| Small Ice Elemental | 1 | outsider | N | Small | ||
| Small Mud Elemental | 1 | outsider | N | Small | ||
| Small Water Elemental | 1 | outsider | N | Small | ||
| Snake Swarm | 2 | animal | N | Tiny | any | Hissing menacingly, this mass of snakes resembles a pile of slithering tentacles. |
| Snapping Turtle | 1/3 | animal | N | Tiny | temperate or warm water or shore | |
| Spinosaurus | 11 | animal | N | Gargantuan | warm forests or swamps | |
| Spirit Naga | 9 | aberration | CE | Large | temperate marshes | |
| Squid | 1 | animal | N | Medium | any ocean | |
| Star-Spawn of Cthulhu | 20 | aberration | CE | Huge | any | A mountainous form, this hideous creature is humanoid in general shape, but its hateful face is... |
| Stingray | 1/2 | animal | N | Medium | warm oceans | |
| Storm Giant | 13 | humanoid | CG | Huge | any warm | |
| Stranglereed | 9 | plant | N | Large | warm rivers or lakes | This tangled mass of thick reeds extends from a bulbous pod split by a wide, thorn-toothed maw. |
| Taiga Linnorm | 19 | dragon | CE | Colossal | cold forests | |
| Tarn Linnorm | 20 | dragon | CE | Colossal | cold lakes and swamps | |
| Terraformer | 7 | construct | N | Large | any | |
| Thalassic Behemoth | 20 | magical beast | N | Colossal | any water | |
| Tizheruk | 5 | magical beast | N | Large | temperate rivers or marshes | This serpentine beast undulates through the water. Its scaly skin and its flesh are clear,... |
| Tojanida | 5 | outsider | N | Medium | any water (Plane of Water) | This creature resembles a cross between a turtle and a crab, with flippers instead of legs, a... |
| Tor Linnorm | 21 | dragon | CE | Colossal | cold volcanic mountains | |
| Trilobite | 1/4 | vermin | N | Tiny | any oceans | |
| Triton | 2 | outsider | NG | Medium | any oceans | This scaly, finned humanoid has an athletic build and blue-green coloration. Its legs end in... |
| Tunche | 17 | fey | CN | Huge | warm forests | Standing on three legs, this creature is a mix of dangerous jungle animals and plants fused into... |
| Tupilaq | 7 | construct | N | Small | any | This small humanoid figure grinds and clatters as it moves, its body carved from bones decorated... |
| Tylosaurus | 8 | animal | N | Gargantuan | any aquatic (Plane of Water) | |
| Undigested | 1/4 | undead | NE | Tiny | any | A jumble of melted bones and skull fragments float amid an oozing brown and yellow slurry. |
| Undigested Swarm | 5 | undead | NE | Tiny | any | This brown-and-yellow sludge appears to be made of multiple smaller globules churning in a... |
| Undine | 1/2 | outsider | N | Medium | any land | This blue-haired, blue-skinned man moves with a liquid grace. His ears are fin-like, and his... |
| Uraeus | 5 | magical beast | LG | Medium | warm rivers | This two-headed cobra flies with a large pair of sleek, black- feathered wings that sprout from... |
| Venomous Snake | 1 | animal | N | Medium | any temperate or warm | |
| Venomous Snake Swarm | 4 | animal | N | Tiny | any | |
| Viper | 1/2 | animal | N | Tiny | any temperate and warm | |
| Vishap | 19 | dragon | N | Colossal | any | This slender dragon is covered in vivid cerulean scales with four powerful wings to match. |
| Vodyanoi | 5 | monstrous humanoid | CN | Medium | any rivers or marshes | This humanoid salamander carries a gnarled staff in one hand. Tendrils drape its chin,... |
| Voonith | 4 | magical beast | CN | Small | any rivers or marshes | This brightly colored, long-necked amphibian has six legs, a fanged snout, and numerous finlets... |
| Vouivre | 12 | monstrous humanoid | CE | Large | temperate forests, lakes, or rivers | One half of this creature is a nude woman, and the other is the front end of a slithering, winged dragon. |
| Wakandagi | 14 | outsider | NG | Large | temperate rivers | This antlered beast combines the features of an elegant deer and a slithering serpent. |
| Walrus | 3 | animal | N | Large | cold oceans | Two long tusks jut from the mouth of this bulky, bewhiskered creature. It walks clumsily on... |
| Water Leaper | 2 | magical beast | CN | Small | any lakes or swamps | This vicious monster has webbed wings, a mouth full of sharp teeth, and a long tail ending a... |
| Water Naga | 7 | aberration | N | Large | temperate aquatic | Slender spines and brightly colored frills stretch back from the human-like face of this massive... |
| Water Orm | 10 | magical beast | N | Huge | any lakes | A reptilian head on a serpentine neck slowly surfaces. Shadows beneath the water hint at a body... |
| Water Veela | 7 | outsider | N | Medium | any water (Plane of Water) | |
| Water Wysp | 2 | outsider | N | Tiny | ||
| Water Yai | 18 | outsider | CE | Huge | any water | |
| Werebat (Human Form) | 3 | humanoid | NE | Medium | warm rivers or marshes | |
| Werecrocodile (Human Form) | 3 | humanoid | NE | Medium | warm rivers or marshes | |
| Whale | 10 | animal | N | Gargantuan | any oceans | This immense whale moves slowly through the water with a grace that seems incongruous, given its... |
| Wizard’s Shackle | 1/2 | aberration | N | Tiny | any water | This eel-like creature has a thick, greasy body and a large, circular mouth full of tiny teeth. |
| Yamaraj | 20 | outsider | N | Huge | any (Purgatory) | |
| Young Black Dragon | 7 | dragon | CE | Medium | ||
| Young Brine Dragon | 7 | dragon | LN | Medium | ||
| Young Bronze Dragon | 9 | dragon | LG | Large | ||
| Young Cloud Dragon | 9 | dragon | N | Large | ||
| Young Gold Dragon | 11 | dragon | LG | Large | ||
| Young Green Dragon | 8 | dragon | LE | Large | ||
| Young Sea Dragon | 8 | dragon | CG | Large | ||
| Young White Dragon | 6 | dragon | CE | Medium |