adventure deep underwater

[da newt]

RAW what are the rules governing underwater adventures? I've found the tiny bit on pg 198 of PHB but that leaves tons of questions. Or, where there is no RAW what do you recommend as house rules?

For context we are playing a published AL mod that is centered around a quest to find a girl who went missing 100 yrs ago when the ship she was on sunk ~70 miles off the coast at a depth of ~1 mile, so go explore the wreck ...

Does the spell water breathing protect you from the crushing pressure and hypothermia inducing cold? If you can breath underwater, can you speak? If you can speak, can you hear others speak? If you don't need to breath (warforged for example) can you speak under water? Can you swim in armor (with your 1200 gp and full backpack)? Assuming you can cast, are spells affected? (like what does WEB do at the bottom of the ocean?) How does a party find a shipwreck in the dark 1 mile below the surface somewhere about 70 miles out to sea?


Or does everyone just handwave everything and go with the rule of cool over realism and pretend to be Ariel for the day?

'you hire a ship and tell the captain to go East ~ 70 miles. When you get there they drop the anchor and you follow it down with your water breathing spell and the wreck is 50' from the anchor. You approach the wreckage and see bad guys onboard so you yell out to your pals and then cast WEB and it works just like it does on dry land. The battle goes OK - your non casters are seriously hamstrung by the weapon and movement rules, but your casters are unaffected. Then you take a short rest to heal/rest before heading below decks ...'

[da newt]

On Earth:

The pressure at sea level is ~ 14.5 psi. The pressure at 1 mile under water is ~ 2500 psi. Modern Navy Subs can't survive these depths.

The temp in deep water is ~ 35 F. The Survival time for people in waters of that temp are ~ 20 minutes exhausted/unconscious, 40 minutes dead.

[stoutstien]

Well like most things they made the underwater environment mostly fiat on the DMs part and the rules they do have are random. Like nets already have permanent disadvantage and bows work just as well as crossbows do.

The DMG has some equally vauge suggestions in chapter 5 like frigid water and becoming lost on top of the underwater section.

[deljzc]

If you want to make an adventure that will have substantial time in this environment, you probably have to homebrew the entire thing.

I'm not even sure the races would all be equal under water.

As much as I love the old-school Greyhawk Saltmarsh adventures, U3 did get hard to manage because that entire adventure is under water. If you can find a copy of Ghosts of Saltmarsh, they might have clarified some rules for that part of the adventure as they upgraded to 5e.

[da newt]

DMG ch 5:

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.



So this published adventure is at a depth of 1 mile (5280ft). So at the normal 30' per turn movement which is halved for non swim speed folks, it would take about 35 minutes to swim straight down one mile. And once you are down there for 25 minutes, you reach your 1 hr point and roll exhaustion saves. How many? Well I guess 2^52 = 4,503,599,627,370,496? So unless your CON save mod is +10 or better, you die (unless you have a swim speed). OR anything over 200' deep doesn't add any more consequence so its just 4 saves per hour. Then (if you aren't dead) after 8 hrs, you can't swim anymore so your speed = 0 until you finish a long rest?

[Dualight]

The rules are silent on how ever increasing depth works, so the 1 hour= 4 is basically at all depths (below 200 feet).
Beyond the 8 hour mark, it seems to get into the forced march, unless there is some place/way to rest down there.
Should be punishing enough, and I doubt that the party will have swim that far, unless they cannot find a ship that is willing to get them to where they need to go and grow desperate. (does the module not provide any guidance on this?)

As far as i know, off the top of my head, the main changes underwater are that combat becomes 3D for everyone, and fire is resisted by everything. beyond that, there are some weapons that work not as well, but everything else functions as normal, unless there is something that makes it logically impossible for it to function (e.g. fog cloud might not work as intended, depending on what the fog consists of).

Someone who knows the rules better/has found a citation will probably be able to correct me where I am wrong.

From faint memories of playing an underwater section in an AL module years ago, most abilities functioned as normal, but we definitely felt out of our element.

[togapika]

After each hour of swimming, a character must succeed on a DC 10 Constitution saving throw or gain one level of exhaustion.

And once you are down there for 25 minutes, you reach your 1 hr point and roll exhaustion saves. How many? Well I guess 2^52 = 4,503,599,627,370,496?

Seems more like it intends 1 roll per hour?

[JackPhoenix]

Water Breathing allows you to breathe water. That's it. It doesn't protect you against anything, and it doesn't give you swim speed. Spells do what their description says they do.
How the party intends to find the wreck is an excercise for them, but considering how harsh the enviroment in such depths is, knowing where something is does not mean they can also get there.
Cold is one issue... Frigid Water rules from DMG seems usable enough. Pressure is another. It's actually somewhat covered by Ghost of Saltmarsh, but the optional rule is not very forgiving: At 2500', the pressure is enough to destroy even adamantine objects, unless they are magical. Visibility is another problem, but that one can be solved easily.

[ImproperJustice]

Handy-Wavy magicy boo….casting water breathing lets you swim at great depths too….

Either that or it’s time to find an apparatus of Kawlaish, a submarine, or begin researching a while new line of spells such as:

Lesser Deep Sea Diving, Deep Sea Diving, Greater Deep Sea Diving, etc….

Although maybe a necklace of adaptation can help here?

I mean, somebody somewhere has got to have some magic solutions for undersea exploration?
Polymorph into Tube Worms, maybe?

[da newt]

The DM has decides to use the easy button: The spell Water Breathing allows you to breath water, speak underwater, hear others speak underwater, and protect you from the cold and pressure. Also the hired ship's Captain is an expert at navigation and can find the exact spot 70 miles from land and drop the anchor within 50' of the wreck.

We are limited by darkness, slow swim speeds, and DISADV for most weapon attacks, but other than that it's pretty much the same as adventuring on land.

I completely understand why we are doing it this way, but also really disappointed that a published adventure doesn't address the 'realities' (yeah, I know, DnD reality is an oxymoron) of finding a wreck in 5000+ Ft of water and exploring it. Doesn't anyone proof read these things?

[Sigreid]

Handy-Wavy magicy boo….casting water breathing lets you swim at great depths too….

Either that or it’s time to find an apparatus of Kawlaish, a submarine, or begin researching a while new line of spells such as:

Lesser Deep Sea Diving, Deep Sea Diving, Greater Deep Sea Diving, etc….

Although maybe a necklace of adaptation can help here?

I mean, somebody somewhere has got to have some magic solutions for undersea exploration?
Polymorph into Tube Worms, maybe?

The party Triton: "Finally, my moment to shine!!"

Also, for getting down there, they don't really need to swim. They just need to hold onto something that will sink with them attached.

[KorvinStarmast]

As much as I love the old-school Greyhawk Saltmarsh adventures, U3 did get hard to manage because that entire adventure is under water. If you can find a copy of Ghosts of Saltmarsh, they might have clarified some rules for that part of the adventure as they upgraded to 5e. No, but there are some other ways to mitigate that if the party doesn't have a druid or cleric who can cast the proper spell. There's an NPC druid who could prepare water breathing for the party if they can talk him into accompanying them to the location; The party I just ran through that had a druid, so he was able to prepare the necessary spell ...

Doesn't anyone proof read these things? I would call something that is a mile down 'unrecoverable' for the genre we are dealing with "Unless aided by powerful magic" and limit anything practically searchable to the 100 fathom curve. (600 feet deep and less ~ heck, it' gets very dark before that depth ... ). But, since fantasy world physics is not by default our world physics ~ it's more metaphysics, see also the odd rules on falling and falling damage ~ there's a lot of roon to wiggle.

And then there's "change shape into a water elemental" which puts a time limit on the exploration since the spell will run out in an hour.

But no, to answer your question, I don't think anyone proofs those things. :smallwink:

[JackPhoenix]

I would call something that is a mile down 'unrecoverable' for the genre we are dealing with "Unless aided by powerful magic" and limit anything practically searchable to the 100 fathom curve. (600 feet deep and less ~ heck, it' gets very dark before that depth ... ). But, since fantasy world physics is not by default our world physics ~ it's more metaphysics, see also the odd rules on falling and falling damage ~ there's a lot of roon to wiggle.

And then there's "change shape into a water elemental" which puts a time limit on the exploration since the spell will run out in an hour.

But no, to answer your question, I don't think anyone proofs those things. :smallwink:

Speaking of metaphysics, a friendly ghost or other incorporeal undead (hexblade's specter?) may be useful. It's not like they have bodies to be crushed by the pressure....

[Kurt Kurageous]

This is a hostile environment.

It's cold. Without ring o warmth or equivalent, that's a no fun.
It's dark. Like underdark dark. Without some light, darkvision fails. Even night vision devices can't see into a location with no available light to amplify.
It's heavy. Everyone is pretty much SLOWed.

Sum it up, without major DM intervention and handwavium, it isn't really a setting so much as a graveyard.

Who's having fun with that?

[JackPhoenix]

It's dark. Like underdark dark. Without some light, darkvision fails. Even night vision devices can't see into a location with no available light to amplify.

Darkvision doesn't need any light.

[Angelalex242]

Use the Kingdom Hearts plan: Turn the party into mercritters if they're going to explore Atlantica.

[da newt]

How do you mer-critter for an extended period of time (enough to swim 1 mile to ocean floor, search for wreckage, complete small dungeon crawl through wreckage, mini-boss encounter, find McGuffin, swim up 1 mile to surface) for a full party?

I like the thought - how do you make it work for 1 full adventuring day?

[Angelalex242]

Polymorph Self/Other.

[da newt]

How do you cover a whole party for one normal adventuring day including combat? What sorts of beasts do you morph into that function at 5000+ ft depth and can complete a small dungeon crawl?

Polymorph: 1 target for 1 hr costs 1 4th lvl spell slot and concentration.
You can twin to cover two folks for 1 hr.

[LudicSavant]

Does the spell water breathing protect you from the crushing pressure and hypothermia inducing cold?

No. However, it seems the DMG suggests that getting a swim speed helps with pressure, and you can get that from stuff like a Ring of Swimming (gives you a 40ft swim speed, non-attunement, just Uncommon -- comparable to a Darkvision item). Any you can get Cold resistance all the usual ways.

[Angelalex242]

Presumably, Tritons or something similar.

Alternatively, hand out armor of the deep to the whole team!

[rel]

How do you mer-critter for an extended period of time (enough to swim 1 mile to ocean floor, search for wreckage, complete small dungeon crawl through wreckage, mini-boss encounter, find McGuffin, swim up 1 mile to surface) for a full party?

I like the thought - how do you make it work for 1 full adventuring day?

The solution is always more dungeoneering.
Go on a quest to retrieve the Keg of Plenty and earn the favour of Broseidon, god of the Brocean.

[Kurt Kurageous]

Darkvision doesn't need any light.

You are correct, in darkness as dim 30'.

[JackPhoenix]

You are correct, in darkness as dim 30'.

Most sources of darkvision have 60' range.

[da newt]

Yes - darkvision is normally 60' but the DMG bit about Underwater Visibility lists these "encounter distances":

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.

Encounter Distance
Clear water, bright light 60 ft.
Clear water, dim light 30 ft.
Murky water or no light 10 ft.

So IF dark vision allow you to see in the darkness as if there is dim light, then 30' from the above?

But then how does dark vision actually work (another thread) - how do you sense heat through COLD water, or echo-locate, or whatever ...

Isn't this fun?

[JackPhoenix]

Yes - darkvision is normally 60' but the DMG bit about Underwater Visibility lists these "encounter distances":

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.

Encounter Distance
Clear water, bright light 60 ft.
Clear water, dim light 30 ft.
Murky water or no light 10 ft.

So IF dark vision allow you to see in the darkness as if there is dim light, then 30' from the above?

But then how does dark vision actually work (another thread) - how do you sense heat through COLD water, or echo-locate, or whatever ...

Isn't this fun?

Completely irrelevant, as the table ignores the existence of darkvision.