What happens when Water Breathing is dispelled underwater?

Question

Suppose someone has the Water Breathing spell cast on them and goes underwater. What happens if Water Breathing gets dispelled, in either D&D 3.5e or Pathfinder?

1. Would he drown without being able to hold his breath since he was using Water Breathing to breathe?

2. Would he be able to take a breath and then try to go back to the surface to get some air?

In the wording of the spell it only says this:

The transmuted creatures can breathe water freely. Divide the duration evenly among all the creatures you touch.

The spell does not make creatures unable to breathe air.

So how would you handle this situation?

Answer 1

I'm neither biologist, swim instructor, nor magician, but according to the rules, a creature who's ability to breathe underwater is negated while that creature is underwater should be allowed to hold his breath instead of immediately starting to drown.

From the SRD:

Drowning
Any character can hold her breath for a number of rounds equal to twice her Constitution score. After this period of time, the character must make a DC 10 Constitution check every round in order to continue holding her breath. Each round, the DC increases by 1. See also: Swim skill description.

When the character finally fails her Constitution check, she begins to drown. In the first round, she falls unconscious (0 hp). In the following round, she drops to -1 hit points and is dying. In the third round, she drowns.

A killer DM might rule that a creature who is unexpectedly put in a situation wherein the creature must breathe water starts to drown immediately as the creature's had no chance to hold its breath, but that's more an issue with the DM than the rules. If you've such a DM, I recommend purchasing a portable hole (DMG 264) (20,000 gp; 0 lbs.), filling it with water, and bull rushing foes into it while yelling, "Surprise!"

Answer 2

By the very wording of the spell, creatures under the effect of water breathing are able to breathe water, that is unless they are on the surface and breathing air normally, their lungs are filled with water (but without them drowning). Biologically, this would among other things not only fail for breathing as the spell wears off, but also cause a laryngospasm, so even resurfacing and trying to breathe air would likely be unsuccessful.
Insofar, sticking to the letter of the definition, you would have to let your players drown immediately!

Of course if you just kill your players because of some sophistries without giving them at least a chance to survive, you are one lousy DM.

Since in the end whatever happens it's the DM's decision, I would rule that the magic effect wears off and the water is removed from the lungs (in favor of air) the same instant, forcing players to hold their breath as normal, starting from that moment. It's magic, after all.
If you want to increase challenge, e.g. if they are in the middle of a battle, you may have them do a reflex save to avoid breathing in water unexpectedly (or breathing out air!), too. But if that one is failed, don't just let them drown either. Reduce the number of rounds they can hold their breath by one half if you will, but still give them a chance to resurface. It's already enough of a bad surprise.

Answer 3

Sounds like it's up to GM interpretation, but it'd have to be a very cruel GM to go with interpretation 1. Give them a chance to get out. Having your Water Breathing dispelled under water is bad enough as it is.

Answer 4

I think the rules you're looking for are under the Swim skill:

If you are underwater, either because you failed a Swim check or because you are swimming underwater intentionally, you must hold your breath. You can hold your breath for a number of rounds equal to twice your Constitution score, but only if you do nothing other than take move actions or free actions. If you take a standard action or a full-round action (such as making an attack), the remainder of the duration for which you can hold your breath is reduced by 1 round. (Effectively, a character in combat can hold his or her breath only half as long as normal.) After that period of time, you must make a DC 10 Constitution check every round to continue holding your breath. Each round, the DC for that check increases by 1. If you fail the Constitution check, you begin to drown.

There's no mechanic for "taking a breath" first, so you would start counting rounds at that point (just as if you had decided to go underwater or failed a Swim check).

(And remember to count rounds where they take a standard or full-round as two rounds against their hold-breath limit!).

Answer 5

Based on the wording of the spell, you could easily interpret that as their lungs still being filled with air. It simply states that they can breathe water, and taken as literally as possible this does not fill their lungs with water; it simply grows gills (real or magical is up to interpretation) on their neck. That's how fish breathe water. Dispelling the spell would simply remove the gills and force them to start breathing air again to survive.

I would give a reflex save if they were surprised by it, or an automatic "hold breath" as a free action if they saw it coming. This spell is really gross if you interpret it as lungs filled with water when they enter or leave the underwater environment.

Answer 6

The fact that the water breathing spell doesn't come with penalties of any sort (you just breathe water like it was air, that's all) is a factor against the idea that lungs just become magically able to extract oxygen from water.

This is because a mammal breathing a liquid looks like this:
http://www.youtube.com/watch?v=ACQr0IZIb5I

(the link states it's water, but there's likely a fluorocarbon compound involved there).

You can see the poor rodent is quite busy trying to breathe, so doing anything else becomes quite difficult.
On the spot Andrew's idea would be the first and easiest to mind, and I second it - the players develop some form of gills which are removed when the spell ends. This means that they can try to hold their breath and reach the surface when the spell ends.
Also, since we're speaking about magic, there are millions of possibilities (they can absorb oxygen from water through their skin, the CO2 in their lungs is magically converted into O2...), all of which offer landscapes on alternatives uses for this spell. Only a few of these interpretations imply that the lungs are filled with water, and they do need a "magic-over-magic" explanation on why characters do not struggle to breathe a liquid in their lungs.

EDIT (yes it was a bit confused): So to make it clear, I would handle it by ruling that the characters' lungs do not fill with water during the duration of the spell, and at the time the spell ends, the characters will start holding their breath, with their lungs full of air. If you want to restrict the use of this spell solely to breathing water, then in my opinion magical gills (as Andrew suggested) are the perfect way to go. If you want to let the players be creative (and the spellcaster more useful), then you can rule otherwise - would you like the spell to be used to enter poisoned water, or a lake of blood, for instance?

Answer 7

I think all the answers so far are right, but what would make it the best for you is to really decide what the 'magic-mechanism' is and work with that. The book being a bit ambiguous, it would be more fun to devise a real explanation to it, or even multiple approaches.

So far it could be : Gills. No problem, Andrew's reflex save for situation. Lungs full of water. Big problems for the players. Also demands unaccustomed users of the spell should be very uncomfortable with both submersion and retching out the water afterwards.

I'll add : A mask which extracts oxygen from the surrounding water. Reflex save resolve. A pipe which has a portal on the surface through which to breathe. Reflex save.