A long time ago there was some guy on EnWorld writing an entire campaign as underwater adventures. He had an extensive underwater setting and everything,

Arduin had air sharks! Thus, I would occasionally grab other underwater monsters and "air-ify" them. Desert octopus! Floating squids!

And don't forget the flying piranha! (thank you James Cameron)

Quote from: Pyromancer;1046382I did an underwater dungeon once, and there are two elements you can use that are unusual: Three dimensional movement, and currents.

I've done something similar with elemental adventures in Planescape.

Quote from: chirine ba kal;1046541I have some giant drifting jellyfish which will feature as 'moving terrain' in Sunday's game.

That sounds awesome!

Quote from: ArrozConLeche;1046096I saw a show where some divers were exploring an underwater cave . It was eerily beautiful, and I could not help but think of cave exploring in D&D.

It'd be fun to do that in a game, but the more I thought about it, the more impractical it looked. You'd need some sort of magic or equipment to go in the water, and then how do landlubbers fight underwater against any creatures who belong in that environment?

Anyone tried anything of the sort?

Yes, I have done this in RuneQuest several times.

The PCs tend to have water-breathing magic, which makes things easier. If not, they have to make a number of CON rolls for each stretch of underwater swimming, with one or more Swimming rolls, failing the CON roll or fumbling the Swimming roll means they start drowning. I sometimes give them a Luck roll to see if they can find a pocket of air at the last minute. PCs can always transfer air ro one another, or keep it in helmets, with a sibstantial modifier to Swimming to keep the air in the helmet.

Squeezes are bad, basically a Squeeze is a tight space that you have to squeeze past. You need to overcome the Squeeze vs SIZ on the resistance Table if SIZ is greater than Squeeze. So, a SIZ 16 person squeezing through a Squeeze 10 has a 10 vs 16, or 20% chance to squeeze through. Each squeeze attempt takes 1 round, a fumble means you are stuck. Heavy armour or equipment adds +1 SIZ. Squeezes are good near the end of an underwater swim, as the PCs already have problems with holding their breath.

Light is harder, Torches and lanterns won't work underwater, so they have to use light-causing magic, have magic items or rely on natural light. If the light is dim, this gives them a negative to combat rolls.

As for combat, they are restricted to their Swimming chance, unless they are natually amphibious. Thrusting weapons are at full chance, as are natural weapons, slashing weapons are at half chance and do half damage, crushing weapons are at half chance and do minimum damage. If they are holding their breath, they can fight for a number of rounds before having to breathe again, I think I use CON rounds. Being hit makes you roll a CON roll to see if you lose your breath. Grappling can force you to make a CON roll as they squeeze the breath out of you.

Quote from: Pyromancer;1046382I did an underwater dungeon once, and there are two elements you can use that are unusual: Three dimensional movement, and currents.

Weapons and spell use should be different as well.

I've done it ONCE and it was waaaaaay more work than I thought it should have been.  And the biggest problem (air) was already taken care off.

Quote from: Doom;1046114Basically you use the ridiculously good 5e Waterbreathing ritual, and handwave all the realistic problems of movement, visibility, equipment use, tweak a few spell effects...and then you have at it for some fun.

Hehe! Sounds about like all the other things that keep me from playing D&D (at least, without a GM who is making things worth playing by doing a brilliant job running everything and basically inventing how everything works him/herself): you use the ridiculous unrealistic thing that's nothing like the situation it's supposedly about, handwave, ignore, and have the DM make up stuff, don't complain or point out anything logical, and "have fun!"

Quote from: Spinachcat;1046669That sounds awesome!

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The 'custom of the house' is that anything coming inside the edge of the base gets a stinging attack.

Oh, and they glow in the dark, too.

Quote from: Chainsaw;1046163I think underwater adventuring can work well as part of a higher-level adventure, basically allowing the players to use their PCs' accumulated abilities, resources and magic items to explore an area previously inaccessible to them and likely permanently inaccessible to most. As such, perhaps it has a disproportionately special and marvelous treasure! Once they get waterbreathing (via spell, device, potion, etc), I would maybe do a very modest penalty to movement/attacking (nuisance caliber, not gimping) and then run it relatively normally. I would try to highlight the fun of exploring the undersea world rather than get bogged down too much in the physics (it could really suck if you're hyper-focused on super realistically modeling movement, vision, spell effects etc). If such a concession makes your head asplode, then yeah, I guess you have to avoid underwater exploration. /shrug

Like many other challenging environs (gas-filled sections of dungeon levels, permanently-burning coal mines, unstable dungeons wracked by recent earthquakes, etc.), waterborne or undersea adventures offer surface-dwellers many risks if they cannot breathe or move well.  Sometimes those risks can be mitigated with spells and magic items (the usual suspects), herbs (gillyweed anyone?), or a proper sacrifice to your friendly local sea (or perhaps air) god.  Sometime strange air-filled pathways and chambers also just lead down below the surface, for indeterminate lengths of time (see Leiber's "When the Sea-King's Away").  If the players or DM are interesting in making aquatic adventures happen, where there's a will, there's a way!

Quote from: Mistwell;1046550A long time ago there was some guy on EnWorld writing an entire campaign as underwater adventures. He had an extensive underwater setting and everything,

That sounds like Aeolius (sp?), who ran lots of undersea Greyhawk campaigns BITD.

Allan.

Quote from: chirine ba kal;1046541The group seems to be having no problems with it; they are using 5e for the rules, I gather, and my depth markers to indicate where everyone is in the water column. The water is arbitrarily decreed to be a 12" ruler's depth; we could go deeper, as I have a second set of depth gauges that are based off of yard sticks. The vertical move on the 12" gauges is set in 2" increments, and the colors provide a visual shorthand for players and GM for things like ambient light and pressure issues. The players and GM seem to like the whole thing, and currents do factor in as movement penalty/bonus modifiers.

The 12" depth may seem shallow, but it seems to provide enough 3D to please people and not slow down the game play. I've played various air combat games in the past, where all sorts of telescoping rods and the like get used, and unless you have pretty experienced players the game can bog down in the presentation mechanics very quickly. I do have short stands for the sea life, but this is for the visual effect on the table more then anything else. I also like to do 'random encounters' just to keep the players on their toes; I have some giant drifting jellyfish which will feature as 'moving terrain' in Sunday's game.

Does any of this help?

That's very helpful. Thanks everyone. That helps me visualize better how one can go about it in a more 'realistic' way.

I've certainly done it, and it's very interesting. But for it to work you either need the PCs to be quite high level or have temporary or permanent access to magic that lets them get there and survive down there.