Underwater Adventures: D&D's Forgotten Realm

Underwater adventures are grossly underutilized in D&D. Even simple nautical or seafaring adventures (where the main mode of wilderness travel is via boat rather than on foot) are relatively rare. There might be the occasional partly flooded dungeon or passage on a ship to the Isle of Dread or Chult, but little of the adventure in D&D seems to take place beneath the waves themselves.

This makes plenty of sense, as players are likely controlling land-dwelling characters like humans, dwarves, elves, or halflings. "Water levels" in video games like Donkey Kong Country, Legend of Zelda, or Metroid (to name but a few) are iconic, but often for the wrong reasons - that is, they're annoying as Hell. Presumably, underwater adventures in D&D would be likewise. 

The AD&D DMG devotes two full pages to play in these environments (which at once seems like a significant amount while also being unfathomably scant). There's a lot to consider in those two pages. There's also a lot to consider beyond them. But look at this introduction:

Ancient submarine civilizations? Creatures half-man and half-fish? Mountains of sunken loot? Pearls as big as a man's head? Beautiful mermaids? I need to go there. Why don't we go there more?

For starters, there are issues like breathing, movement, vision, combat, and spell use to consider.

 Underwater breathing can be achieved by spells, potions, magic items, or other contrivances invented by the DM for the occasion:

Since the ability to breathe underwater is time-limited, underwater adventures are assumed to be akin in scope to dungeon adventures, rather than wilderness adventures. What I'm imagining is the characters piloting a boat above some sunken ruin, casting all their spells or chugging their potions, and diving in for a short expedition. While all dungeons have time pressure in the form of random encounters and available light sources and provisions, underwater adventures take this to the extreme. If you can't get out in time, you die.

(Add "comestible" to the list of words I learned from reading D&D.)

Just as underwater expeditions are similar to dungeon adventures in terms of duration, they are also similar in terms of movement:

When adventuring underwater, characters use their dungeon movement rate. A character with a movement rate of 12" can move 120 yards per turn outdoors on dry land or 120 feet per turn in a dungeon on dry land. Underwater, they likewise move 120 feet per turn. This assumes that underwater adventures are basically "outdoors".

How quickly then does the character move in an underwater dungeon? It isn't clear. Since your "outdoors" underwater movement rate is equal to your dry land dungeon movement rate (itself one-third of your dry land outdoor movement rate), I would personally rule that your movement rate in an underwater dungeon is likewise one-third your dry land dungeon movement rate. So, a character with a movement rate of 12" would move 40 feet per turn in an underwater dungeon. Sounds pretty reasonable to me.

Swimming is only possible when the character is wearing leather armor or lighter and is carrying fewer than 20 pounds. That's not a lot of equipment! Then again, you probably don't want to get most of that equipment wet anyway. Even magic equipment like a ring of swimming does not permit swimming if these conditions are not met.

Swimming introduces another unique element of underwater adventures - swimming characters are vulnerable to attack from every direction. Underwater adventures are more three-dimensional than land adventures because, outside of flight or levitation, characters don't usually have such unfettered access to that third dimension.

This section also gives us a hint at what sorts of environments or terrain are found underwater - hills, coral outcroppings, shipwrecks, seaweed forests, and the like. Note that swimming without the aid of free action magic does not allow you to move faster than someone forced to walk along the ocean floor, but it does allow you to swim over or around these obstacles.

Next is vision:

There are basically "simple" rules for vision (you can see X' until you reach a depth of Y', at which point the environment is treated basically as darkness) and "complex" ones. (you can see X' when 10' below the surface, but X decreases by 10' for every 10' you descend). 

Underwater environments complicate infravision because the temperature of the water is varied by shifting currents. Seaweed, schools of fish, and mud can obscure vision. Sea grass can be up to 30' tall and clouds of mud can persist for up to 12 rounds!

Then we have combat considerations:

Without free action magic, only the use of thrusting weapons is possible, and natural swimmers will always strike the first blow against landlubbers unless a weapon with reach is employed. 

This is where nets (themselves the unsung heroes of the D&D weapons list) will shine. Characters can throw a net only a number of feet equal to their Strength score, and suffer -4 to hit with them unless they've trained extensively (underwater!) with the use of such a weapon. 

Specially-made crossbows costing ten times the normal amount can also function underwater. If an underwater adventure is to transition to one in an airy environment ("like the great air-filled domes of Atlantis"), bows, missiles, scrolls, and other items must somehow be kept dry.

We also get a taste of what creatures might be encountered in the water - aquatic elves, locathah, mermen, and the true terrors of the deep, sahuagin. The latter employ clever and dastardly net traps in their ambushes.

Finally, spell use:

Like most everything else, spells function as they do in dungeons, with a few caveats. Some material components will not function underwater. Fire-based spells will only function in airy water, and electrical spells will affect the entire area. I imagine it would also be difficult to make the precise gestures required by somatic components (unless magically capable of moving freely) and to speak verbal components (unless in airy water or maybe if magically capable of breathing water), but this isn't stated.

There is a sizeable list of spells that won't function underwater or will only function in airy water (marked by an asterisk):

Many of these are fire spells, but there are other notables - spells which summon insects, and spells dealing with air, wind, or the weather. Animal summoning is curious - could the caster not just summon aquatic animals instead? I imagine this is because the spells and their tables assume that adventures will be happening on land. Still it would be nice if alternative underwater tables were provided. You can't summon a cacodemon or woodland beings, but you can apparently cast monster summoning. Unlike animal summoning, the monster summoning spells do get their own underwater tables:

Also of interest is that spells that require speaking (speak with dead, speak with plants) function only in airy water, which seems to suggest that unless air is present, speaking is not possible. So then wouldn't any spell with verbal components not function without air as well? That's like, most spells. Curiously, speak with animals is omitted. 

I would probably say that if you can breathe underwater, you can speak (and utter verbal components) underwater. If you are capable of swimming (either due to being unencumbered by armor and equipment or by way of magic), you can perform somatic components. Easy peasy.

Then there are a handful of spells which are specially altered when cast underwater:

My favorites have got to be wall of ice (the entire wall simply floats to the surface) and Otiluke's freezing sphere (the caster entombs their self in a sphere of ice, which floats to the surface, and they suffocate unless freed).

This all sounds like a bit of a headache for the DM and players alike, and that's because it is. Underwater environments are alien - more alien even than the dungeon. The deep ocean is probably the most alien place on our own planet Earth. It makes sense why so few adventures take place underwater. Adventuring there should be hard, because the characters aren't from there. But what if they were?

The allure of underwater adventures, in my opinion, is not brief expeditions to sunken dungeons (although that is certainly one of the lures), it's the ancient civilizations and the creatures half-man and half-fish - the aquatic elves, locathah, mermen, sahuagin, and the like. There are vast empires (or probably more accurately in most cases, pretty large isolated ethnic enclaves) beneath the waves, and they are inhabited by all sorts of aquatic people. Can't the players play as one of those people?

Let's start by looking at the underwater encounter tables. These are broken into shallow water (where vision is relatively easy) and deep water (where light from above does not penetrate), and into fresh water and salt water. Who says your underwater adventures have to take place in the ocean?

Interestingly, the paragraph before the tables suggests that the "Number of creatures encountered should be appropriate to the strength of the encountering party":

Hmm...Here I thought old school D&D was supposed to eschew balance (which is maybe true - some true believers don't consider AD&D "old school"). While this same sentiment isn't reiterated prior to the land-based wilderness encounter tables, I can't imagine why it would apply only to underwater encounters. File this under "Important rules mentioned once in passing in a random section of the DMG".

Anyway, I will admit that the fresh water encounter tables do not suggest some larger civilization of which the player characters might be a part or might engage with. It's mostly animals and unintelligent monsters:

Hobgoblins and lizard men are certainly playable races in later editions of D&D. There are some other intelligent monsters in here like giant beavers, gargoyles, ghouls, naga, nixies, and nymphs, but none of those exactly read as playable races (though a giant beaver campaign would be sick). Interestingly, dinosaurs are on the list, despite being found on land only in "Pleistocene Settings". Even if your AD&D world overall is not populated by dinosaurs, they will still dwell in your rivers, lakes, and oceans!

The deep water table is more of the same, though it eschews a few monsters (regular crocodiles, giant frogs of all kinds, green slime, hippopotami, regular lampreys, giant leeches, and nymphs) in favor of others (giant water beetles, dragon turtles, storm giants, giant lampreys, and purple worms). It's cool that the deep lake next to town might have a dragon turtle, a purple worm, or a storm giant's castle at its bottom.

The salt water tables are a bit more interesting:

Here are the aquatic elves, locathah, mermen, and sahuagin. They are joined by ixitxachitl, sea hags, triton, and more nasty sea creatures, plus many of the same interesting creatures from the fresh water tables like storm giants, hobgoblins, gargoyles, ghouls, and nymphs. The deep water table adds the eye of the deep (a deep sea beholder) and one of my favorite weirdos, the morkoth.

Underwater environments in AD&D are full of nasty monsters that leap out of hiding to eat you, swallow you whole, capsize or sink your ship, poison you, paralyze you to be eaten, stun you with light or trick you with illusions to tear you apart with their crab claws, torture you, melt you, suck your blood, enslave you (but only for one year!), and blind you or kill you by looking at you or by getting nude in front of you.

Like many of AD&D's environments, underwater is not a nice place. But these environments are also home to intelligent beings with their own societies. 

10% of dolphins form underwater communities of 4 to 100 dolphins with swordfish and narwhals as trained guards. Storm giants live in spacious castles beneath the waves and keep sea lions as pets (for whatever reason, all of their magical abilities are those select spells which explicitly do not work underwater). Koalinth (aquatic hobgoblins) fulfill much the same function as their land-dwelling counterparts. Ixitxachitl lair in secret coral reef caves and can be clerics of as high as 8th level. Some of them are vampires. Locathah live in hollowed out castle-like undersea rocks, ride eels into battle, and use Portuguese men o' war as traps (implying the existence of Portugal in the default AD&D setting). Water naga are curious creatures capable of casting spells as 5th level magic-users.

Aquatic elves are much like land-dwelling elves (with whom they engage in trade), but they are allies of dolphins and mortal enemies of sharks and sahuagin. There are wars being waged beneath the waves! They dislike fishermen because the elves get caught in the fishermen's nets, are mistaken for sahuagin, and killed.

Mermen live in undersea communities among the reefs and cliffs, sometimes constructing villages of shells, rocks, and coral. They herd fish, have their own workshops, and keep barracuda as pets. Oh, they also form raiding parties to grapple surface ships en masse and slowly drag them down to the bottom of the sea to be looted, killing everyone aboard in the process. Huh.

Sahuagin get more than a full page all to themselves. They are devil-worshippers and dwell "in a vast undersea city" ruled by a king. The city is built in an undersea canyon lined with palaces and dwellings. 5,000 sahuagin dwell there with 1,000 queens, concubines, nobles, and guards in the king's retinue. The king rules nine provinces (mirroring the levels of Hell), each ruled by a prince. The princes live in strongholds, while most other lairs are "actual villages or towns, constructed of stone" and hidden among the seaweed. 

They align themselves with sharks, venture onto land to raid, and hate even the evil ixitxachitl. They have a matriarchal religious structure with clerics of up to 8th level. 1 in 216 (2+1+6=9?) - including the nine princes and the king - is a mutant with four fully functioning arms. Those they capture are either tortured and eaten or made to compete in blood sport, dying either way.

They are either distant relatives of the sea elves created by the drow, or some Lawful Evil god created them from humans "when the deluge came upon the earth." I'm sorry - I wasn't aware of The Deluge! This is rich stuff.

Triton live in undersea castles and sculpted caverns, can become 6th level magic-users, and keep hippocampi, giant sea horses, and sea lions as pets. They can use their conch shell horns to summon these creatures to their aid and panic unintelligent sea creatures. Some have psionic ability. They are from the Elemental Plane of Water and "have been planted on the Material Plane for some purpose presently unknown to man", engaging in wars with sahuagin, ixitxachitl, koalinths, and lacedons.

There's a lot going on underwater! It's dangerous and comes with a great many complications, so I can see why humans, land elves, dwarves, and halflings aren't exactly eager to board a ship and risk getting sunk by a dragon turtle, giant squid, or raiding party of murderous mermen, let alone actually go diving down there to contend with these horrible creatures in such an alien environment. That doesn't mean we can't have adventures there.

I could see a campaign where the player characters are aquatic elves, locathah, mermen, tritons - hell, even koalinth or sahuagin - plundering the ruins of their own ancient civilizations as well as the sunken remains of the civilization above, building undersea strongholds among the coral and cliffs, and getting mixed up in factional politics and aquatic warfare. There are still dungeons there, and dragons, too (in turtle form, at least) - the only two things you really need for a D&D campaign.

A campaign in such a drastically different environment would need to have many considerations. Being able to swim freely underwater is akin to every creature having unlimited flight. I imagine no one is wearing armor. How do potions and scrolls and spellbooks work? Have the magic-users of the undersea realms developed an underwater version of fireball that cooks you alive in a blast of boiling water? That sounds pretty neat.

I need to go there. Why don't we go there more? Why aren't we there right now?