How does the Necklace of Adaption's bubble of air work out in practice underwater?

Question

A recent question about the necklace of adaptation reminded me of an old question of my own that I've never been able to answer: Can a character wearing a necklace of adaption swim?

It might seem a bit of an odd one, but - Well, here's the two sides of the argument, as I see it:

On the one hand, the necklace surrounds whoever wears it with breathable air. Breatheable air isn't really a medium most adventurers can swim through, so it seems reasonable that an adventurer who puts on a necklace and then jumps out of their boat would find themselves surrounded entirely by air on all sides - and so immediately falling to the lake bottom, the water beneath them continually replaced with more empty air for them to fall through. (Presumably, they'd also emit a great plume of bubbles once underwater as air escaped from their continually-replenished personal air supply.)

On the other hand, the bubble is described as a "shell" of air; Maybe the intent is that a "shell" surrounds the adventurer like some kind of suit, and "sticks" to them instead of bubbling up? If that's the case, I feel like maybe the adventurer would float and able able to swim as normal - or rather, to "fly" inside their bubble - since force would transfer from them, to the bubble, and thus to the water that surrounds it, and vice versa. But that also seems weird, since you'd expect the shell of air to also repel other objects, including adventurer's own clothing and equipment and the ground, and that seems like too important a detail to leave out of the object description.

As a GM, I tend towards simulationist play styles where players are rewarded for coming up with creative uses for magic items - but to do that, I need to have some idea as to how those magic items work.

Is there any text that clarifies how a necklace of adaptation does its thing? Can an adventurer wearing one swim, or are they instead able to walk along the lake bottom? Either option sounds plausible and useful. Which, if any, is correct?

I'm tagging this with 3.5e because that's a game I'm currently running, but I'm willing to accept content from earlier editions if there's nothing available from 3.5rd edition. I'll also accept descriptions of functionality from published novels set in official campaign settings, for that matter.

Answer 1

As said by others, the problem doesn't arise if you think it's a bubble head scenario or a thin suit of air. The problem seem to arise when you think of the air around you as something more like the shape/size of the "core" aura of Dragon Ball characters.

So let's go through things:

• Bubble head: Good solution, but unrealistic: the necklace protects the wearer from toxic fumes, so a bubble head would not protect you from acid fumes that would burn the rest of your skin. Unrealistic interpretation, discarded.

• Thin suit of air: If this is the case, then you'd be able to swim normally.

• DB-like aura: now things get interesting. There are two options about HOW the necklace works, and they affect the result dramatically:

  • Option 1: The necklace magically transmutes the medium around the wearer into clean fresh air: This is bad. You are basically creating a space devoid of water that is now air, the density changes a lot, you fall down (and, since your maximal speed in air is greater than in water, you'd slam on the ocean floor and take a lot of dmg if you jump out of a boat).

  • Option 2: The necklace basically makes you "wider": only fresh air and no other medium can exist in 30cm around you. This is actually interesting: you have just gained a LOT of water floating power! As per Archimede's principle, you are now moving a lot more water, which is heavier than air, so the upwards resulting force is stronger than without the necklace! Since you can float without it, you can float even better with it! Though normal swim movements would likely be impaired by the unusual situation, but compensated by your increased surface (your increased surface acts like flippers). In this case I'd rule out that you swim at your normal swimming speed, but are twice as hard to sink.

Bottom line: it depends on how you define the necklace's working! Or, even better, take note of these ideas, then let the player describe the act and punish/reward him accordingly :)

Answer 2

They can swim and walk on the lake bottom

Your question states that you are open to answers from earlier editions. Here is the AD&D 1e version of the very same item, straight from Gary Gygax:

This chain will resemble a medallion. The wearer will be able to ignore gases of all sorts which affect creatures through respiration, breathe underwather, or even exist in airless space for up to 7 days.

No air bubble to be seen. (Neither does 5e have one, for that matter).

From a playability perspective, this also must be the answer for the 3.5 edition of the game: the objective of the necklace always has been and still is to allow the bearer to breathe without issues, not to make them unable to swim or force them float up to the surface or drop to the bottom of a water body.

The 3.5e text says:

This necklace is a heavy chain with a platinum medallion. The magic of the necklace wraps the wearer in a shell of fresh air, making him immune to all harmful vapors and gases (such as cloudkill and stinking cloud effects, as well as inhaled poisons) and allowing him to breathe, even underwater or in a vacuum.

The stated game effects of being wrapped into a shell of fresh air are given as: making him immune to all harmful vapors and gases [...] and allowing him to breathe, even underwater or in a vacuum. That you can breathe underwater is a further indication that you should be able to use this when adventuring underwater, and being unable to swim would directly counter this purpose. If this item would want you to not be able to swim, it would need to list that as one of the effects of the air shell.

When you ask how this effect is achieved, in 3.5 the shell of fresh air is a pesudo-scientific explanation as to how, and one that is not really that helpful. The other editions do not bother -- it's magic, that is how it is achieved. That the air shell does not hold up to scrutiniy from a physics perspective is no wonder: D&D is not a physics simulation. None of the physics behaviours you are asking about are described in the feature as game effects, they are inferred by you from applying modern day knowledge and logic. The other editions confirm that the air shell and its potential physics consequences are not material to the function of this item.

So, if a character can swim, or walk on a lake bottom (which they can under the rules), then all the necklace does is make sure they can breathe while doing so.

Answer 3

Compulsory flippant answer

Here is your problem:

Magic does not follow the rules of science. That is why it is magic!

More temperate rules based answer

Notwithstanding, the default assumption in a FRPG is that the rules of science work until the rules of the game tell you they don't.

1. People in the real world can swim in water therefore people in the FRPG can swim in water. People have, on average, a specific gravity of 0.98 compared to 1.0 for fresh water or 1.025 for sea water, which is why we can swim Human Swimming. Specifically, a living human (i.e. with air in their lungs) will float and this is why divers use weight belts. Now, the deeper you go the denser the water gets so for any object there is a depth where they have neutral buoyancy - for things like steel and rocks this depth may be lower than the ocean floor but there is a cool adventure idea here of the layer of the shipwrecks - sailing at the point of neutral buoyancy.

2. People in the real world can't breath water therefore people in the FRPG can't either. As a consequence of this there are the conditions "drowning", followed by "unconscious" followed by "dead".

So, along comes a Necklace of Adaptation which changes the rules of science by adding some rules of magic. What it says on the tin is (DMG p.63):

Necklace of Adaptation: This necklace is a heavy chain with a platinum medallion. The magic of the necklace wraps the wearer in a shell of fresh air, making him immune to all harmful vapors and gases (such as cloudkill and stinking cloud effects, as well as inhaled poisons) and allowing him to breathe, even underwater or in a vacuum.

Adopting the WYSIWG principle, it does what it says and nothing else.

You are wrapped in a "shell of fresh air"; the only sensible definition of "shell" (Oxford Dictionaries) in this context is "something resembling or likened to a shell because of its shape or its function as an outer case" where the self-referenced definition is "the hard protective outer case of a mollusk or crustacean". Interesting that it doesn't note that some reptiles have a shell too.

The specific gravity of air (compared to water: typically this is usually referenced to air but we have to keep the same units) is 0.001225. So when you add air to anything you make it more buoyant; this is in fact how ships and submarines made of steel actually float. Since floating = swimming, the necklace will make it easier to swim but harder to dive.

Answer 4

I am not entirely sure on which of the definitions are correct,

But in my few hours of scouring, I did find a NPC character called "Lord Calvin Longbottle, Regent of the Harbour" in a 2nd edition book, "Gateway to Raven Bluff, the Living City". Formerly a seaman and now a harbourmaster, he has four magical items equipped and three of them are related to the sea.

1. The Necklace of Adaptation
2. A Ring of Swimming

This has a list of abilities in 2nd Edition, so I will quote an excerpt from the 2nd edition Dungeon Master's Guide:

Ring of Swimming: The ring of swimming bestows upon the wearer the ability to swim at a full 21 base speed. (This assumes, of course, that the wearer is clad in garments appropriate for such activity.) The ring further enables the wearer to dive up to 50 feet into water without injury, providing the depth of the water is at least 1_? feet per 10 feet of diving elevation. The wearer can stay underwater for up to four rounds without needing a breath of air. Surface swimming can continue for four hours before a one hour (floating) rest is needed. The ring confers the ability to stay afloat under all but typhoon-like conditions.

3. An Earring of the Sea (which allows speech towards all sea creatures once a day for 10 minutes).

Although the information written about the items in the Raven Bluff book is scarce (literally one line for each item), personally I think that the Necklace of Adaptation must function like your second definition of it: the Ring of Swimming won't have a use if the Necklace of Adaptation could only be used to sink to the sea floor: for the Ring of Swimming to be useful then, Lord Longbottle would have to take off the amulet, then enter the water, which seems largely redundant.

I'm sorry that I couldn't provide a concrete answer to your question, but I hope this helps even somewhat in this argument.

Answer 5

I would say this is a house-rule situation. Two suggestions for the ruling

Bubble Head

As the description only specifies "the wearer" and not anything further, it could be reasonably assumed that instead of a shell of air around the entire character, the shell of air actually just actively exists around the head, or even just the mouth and nose. Hence, the necklace is basically just a scuba mask, and the character can swim as normal.

Diving without a suit

If you prefer it to be a "walk along the bottom" solution, the shell of air extends a very short distance from the character. In this case, the weight of the character and assorted equipment means that the character can walk across the bottom of the body of water. Due to water resistance, the character acts as if on land but slower, rather like being in a heavy diving suit.

Answer 6

Choose the consequences

I do not believe that there is a definitive interpretation available, which means that we need to look at the consequences of the available options. Let's look at the consequences of a very literalist interpretation of "wraps the wearer in a shell of fresh air".

There will always, at every instant, be a layer of fresh air molecules surrounding the wearer's body. It does not matter how this is happening, the consequences include:

1. The wearer of the necklace cannot be struck by any physical weapon - since that would mean that for some measure of time the "shell of fresh air" would be breached by the weapon that struck the character.
2. Part of the physical invulnerability includes attacks by acid, since this inflicts damage by coming into contact with the skin and a never-broken shell of fresh air cannot be breached.
3. The wearer of the necklace is unable to touch any object, gain traction on any surface and/or consume liquids or food, since a "shell of fresh air" provides insufficient friction to grip objects and will not allow objects from the outside in. There is also the question of whether the Necklace of Adaptation itself can breach the "shell of fresh air" to touch the wearer's skin - maybe it constantly flickers on-off-on-off as the necklace momentarily touches the skin and is suddenly repelled by the layer of fresh air, at which point it is no longer considered "worn" and the shell disappears, at which point the necklace can touch the skin... and so on.

This interpretation requires the wearer to remove the necklace to do most day-to-day activities, but makes them invulnerable to all physical threats while wearing it, which is ridiculously overpowered for a 9000 gp item. So, let's look at what is needed to make it less overpowered, at which point we can look at the consequences for a character swimming.

First, I suggest that invulnerability to all physical threats is out, as is an inability to interact with objects. So, the general rule must be that solid objects can penetrate the shell of fresh air without any significant effort except where they would interfere with breathing. The character can be hit with fists, swords, arrows and anvils, and can even have their skin sand-blasted off, but being buried in sand will not suffocate the character because that would contradict the spirit of the "allowing him to breathe, even underwater or in a vacuum."

Second, liquids can penetrate the shell of fresh air without significant effort, since otherwise the character would be unable to drink and would be invulnerable to acid damage. (They would also be unable to bathe, although the constant shell of fresh air would prevent anyone noticing the odour.) The only point at which liquids get stopped are where they prevent breathing.

This means that the character can swim normally. The alternative is that the item provides protection from liquids such as acid or boiling oil, which is not part of the Necklace of Adaptation's stated benefits.

This interpretation means that the wearer is wrapped in a shell of fresh air, which is not impenetrable - the description never said it was - but will displace all other gases that would come into contact with the wearer, along with any solids or liquids that would interfere with breathing.