Dealing with the pressure of underwater pressure..

[Three_Haligonians]

Stormwrack rules on deep sea pressure is a simple 1d6 damage per 100ft deep per minute of exposure. This sounded fine for my game until I realized it was taking place on the ocean floor which, taking a cue from RL, is close to 12,000ft down. That clocks in at 120d6 dmg per minute of exposure! Even though I'm running a game for a group of 6 30th lvl characters, that kind of damage will certainly take them out quickly.

Stormwrack also provides spells that will take care of that problem, making characters immune to pressure damage and whatnot. The problem is my players are smart - too smart in fact because when they realized that they would be dependant on spells and magic to breathe underwater, they realized they would be vulnerable to dispel magic and similliar effects from the enemey and then they realized that their "pressure protection" would be vulnerable as well.

There are a few non-magical ways to get air under the sea that they can learn about and get access too and in fact, we'll have some fun when the villains do indeed dispel their water breathing - that's easy, they have some time before they drown to save themselves.

But what of the pressure? Are there any non-magical ways to get used to deep sea pressure? If they lose that protection, chances are the first incursion of damage will kill them (unless I roll really low on my 120d6 damage).

Any thoughts?

J from Three Haligonians

 

[Jack Simth]

At 1d6 per minute per 100 feet at 1200 feet, that would be 12d6 per minute, not 120d6, unless you mistyped something, and meant to go with 12,000 feet, or 12d6....

But as it takes 10 rounds for it to matter, simply arrange for them to have multiple copies of the spells, or have the spells from wondrous items (dispel magic only puts them down for 1d4 rounds, or some such - much less than the fatal 10). If combat isn't over in 10 rounds, you're probably losing anyway.

 

[Three_Haligonians]

At 1d6 per minute per 100 feet at 1200 feet, that would be 12d6 per minute, not 120d6, unless you mistyped something, and meant to go with 12,000 feet, or 12d6....

Yep, your right.. it was a mistype. I forgot a 0, funny how it makes such a difference.

Thanks,

J from Three Haligonians

 

[green slime]

In RL, you don't take damage from pressure underwater per se. It is some kind of popular myth that the pressure causes great damage. The only damage that will occur is in air-filled spaces, because a gas under pressure will reduce its volume. As most of the body consists of water, and some solids, nothing will happen, if the diver "equalises", in a manner similar to travellers flying in a plane coming in for landing must equalise or risk a painful ear (it may even rupture).

There are other, greater dangers when exposing yourself to great pressure; the normal air you breathe becomes toxic (happens around 90m or 300 ft, because the partial pressure of Oxygen approaches 2.0). Other interesting things happen with the other gases as you go deeper (massive amounts of Nitrogen dissolve into the bloodstream, potentially exposing you the "bends", should your ascent be too rapid).

As I assume you are using water breathing, then most of these problems with various gases disappear.

The biggest problems at those depths in a DnD world would be lack of light, the immense cold, (water disperses heat far more effectively), communication, and underwater currents. And on the sea floor, the risk of stirring up silt and reducing visibility to 0. Most sea floor is not sand.

 

[Pinotage]

In RL, you don't take damage from pressure underwater per se. It is some kind of popular myth that the pressure causes great damage. The only damage that will occur is in air-filled spaces, because a gas under pressure will reduce its volume. As most of the body consists of water, and some solids, nothing will happen, if the diver "equalises", in a manner similar to travellers flying in a plane coming in for landing must equalise or risk a painful ear (it may even rupture).

There are other, greater dangers when exposing yourself to great pressure; the normal air you breathe becomes toxic (happens around 90m or 300 ft, because the partial pressure of Oxygen approaches 2.0). Other interesting things happen with the other gases as you go deeper (massive amounts of Nitrogen dissolve into the bloodstream, potentially exposing you the "bends", should your ascent be too rapid).

As I assume you are using water breathing, then most of these problems with various gases disappear.

Good points. Although I don't agree with the no damage from pressure thing. Free divers certainly suffer significant damage when diving too deep - in fact, you depth is limited by how much pressure your body can sustain. It's very dangerous to dive too deep. At an increased pressure of 1 bar (1 atmosphere) per 30 ft. depth, too deep can be a significant pressure if you're breathing air. You have a lot of air spaces in your body - lungs being only one of them - too much pressure there can cause all sorts of problems.

Nevertheless, in a fantasy world with Water Breathing, I've always ruled increased resistance to pressure effects underwater since you're breathing water now, and not air.

Pinotage

 

[Three_Haligonians]

So how about this..

Taken what was said (thanks for your insight by the way.. I knew someone would know of such things..) I think I might say that characters can acclimatize themselves to deep sea environments so that, much like in high altitudes, as long as they spend time "getting used to" the new depth before continuing, they will be ok (save, of course, for needing to breathe underwater).

This sound reasonable? Am I missing anything obvious? How long should one have to stay at a certain depth before continuing safely? How long can the increments of depth be?

J from Three Haligonians

 

[Pinotage]

Taken what was said (thanks for your insight by the way.. I knew someone would know of such things..) I think I might say that characters can acclimatize themselves to deep sea environments so that, much like in high altitudes, as long as they spend time "getting used to" the new depth before continuing, they will be ok (save, of course, for needing to breathe underwater).

This sound reasonable? Am I missing anything obvious? How long should one have to stay at a certain depth before continuing safely? How long can the increments of depth be?

J from Three Haligonians

This is purely a rule I used in one of my games:

For air breathers, pressure effects start at 150 ft. You take 1d6 damage per minute with the usual saves and checks. You can't dive deeper than 450 ft.

For water breathers (non-aquatic via spell or other) pressure effects start at 450 ft. You take 1d6 damage per 10 minutes with the usual saves and checks. You can't dive deeper than 1350 ft.

For aquatic creatures pressure effects starts at 1350 ft. You take 1d6 damage per hour with the usual saves and checks. You can't dive deeper than 4050 ft.

It's simplified a little from a depth perspective, i.e. you don't take more damage because you're deeper or per 100 ft. as in Stormwrack. But it includes rules for water breathing and aquatic creatures. You can of course, adopt the rule that per 50 ft. or per 100 ft. increases the damage, or even increases the save DC.

Pinotage

 

[SockMonkey]

Hi just stumbled on this thread which is intresting. The rule in stormwrack is rediculous, GS has it right for the most part, there are a few injuries/disorders that one can pickup from pressure.

The human body for the most part can handle direct pressure pretty well the problem arises when the outside pressure differs from the inside, this causes a barotrauma. (rule if they are breathing normaly no issue hold breath= damage. Breath water lungs are filled with water and there is no issue at all)

Barodontalgia AKA tooth squeeze is uncommon but possible at high pressures

Aceptic bone necrosis- Bad one but rare caused by repeated exposure to pressures this one weakens and destroys bones partcularly the long bones.

High Pressure Nervous Syndrome - This one seems the most realistic as far as damage goes and it could be where they were getting the idea from. At dives GREATER than 600 feet of sea water HPNS can occur and it gets worse the faster the rate of compression and greater the depth. Symptoms include dizziness, nausea, vomiting, "twitching and jerking" fatigue, loss of motor function, loss of intelectual faculties and later on loss of sleep and nightmares. If I were to impose a rule it would be more status effects for this one for ranges of like 600-1200 and then perhaps damage after than..

O2 poisoning and hypothermia would be the biggest issues during most underwater quests but lets not forget this is a fantasy setting with magic and all sorts of things that "wouldnt happen in real life"


Incase any one was wondering im a commercial diver, and thats where i got my facts.