If the Sleep spell is cast on an opponent in water, do they immediately start suffocating?

Question

From the description of the Sleep spell:

falls unconscious until the spell ends, the sleeper takes damage, or someone uses an action to shake or slap the sleeper awake.

From the rules on suffocating:

A creature can hold its breath for a number of minutes equal to 1 + its Constitution modifier (minimum is 30 seconds).

When a creature runs out of breath, it can survive for a number of rounds equal to its Constitution modifier (minimum 1 round). At the start of its next turn, it drops to 0 hit points and is dying.

Key point of the unconscious condition:

Incapacitated (can't take actions or reactions), falls prone

So let's assume Margorie the Mage casts sleep on Randy the Robber (Con 10) who just attacked her in a roman bath. Is it correct to assume that, being incapacitated, he would not be able to hold his breath when he fell prone and his head went underwater, and he would begin to drown after one round, effectively dropping him to 0hp?

Answer 1

Probably not?

D&D 5e breaks from the tradition of several more recent editions of D&D by allowing - indeed, encouraging - DMs to make their own rulings on situations rather than following a single explicit canon in regards to the rules. It also - particularly in regards to spells - attempts to be descriptive (of the general effects and feeling of the spell) rather than prescriptive (giving an exact, itemised letter-of-the-law list of the spell's results) and so leaves many details of precise interpretation up to individual rulings.

The sleep spell, in this instance, lists:

falls unconscious until the spell ends, the sleeper takes damage, or someone uses an action to shake or slap the sleeper awake.

A purely prescriptive reading would suggest that this means exactly what it says - the sleep spell causes the target to fall unconscious until one of those three precise things occur. It doesn't matter if someone tries to wake the sleeper up by pulling on their hair or putting a wet cloth over their face; it doesn't matter if there's an earthquake or someone blows a trumpet in their ear. They wake up when shaken or slapped (by someone spending an action, not by any natural phenomena), the spell ends or they take damage.

A reading more in line with the spirit of the rules, on the other hand, suggests that sleep sends you into a deep magical slumber - but one that can be awoken from. What exactly it is that wakes a person from the slumber is up to the DM - but something on the same general level of violence as slapped or shaken would do. I personally would probably count falling into cold water to be enough. But maybe not if, say, the target is a merfolk or something.

This is absolutely a decision that should probably be made as it comes up in game. Maybe, as suggested by bacrossland's answer, after the spell has just been cast, with the conceit that the character didn't know whether or not water would be enough to wake the target - but be aware that this could seem unfair to a player who expected that their character would know whether the spell would work or not.

Cold or warm water?

Is cold water enough to wake someone up in general? Yes, assuming they're capable of being woken up (e.g, they're not exhausted because they've been swimming for days). But warm water may not always be as effective. The key thing to consider here is the mammalian diving reflex - it causes several changes to metabolism, breathing, and almost certainly wakes the sleeping, and it triggers from cold water on the face region. This is why splashing your face with cold water in the morning not only wakes you up, but makes you feel refreshed. It doesn't apply to warm water. Again, DM's call based on a general understanding of biology / decision about magical slumber as to whether Randy would be woken up in the warm or the cool section of the Roman bath - just giving you some background biology information here.

Answer 2

Randy would be out cold for the round and not be able to hold his breath. Holding ones breath is a conscious action and since he was rendered asleep he would not have time to take that breath and hold it. Even if he was holding his breath the second he feel asleep he would let go of that held breath.

Would he drown? SevenSidedDie is correct that Randy would not drown on the round he was asleep. He would start on the next round. The rest would depend on the DM and the situation. A DM can make an easy argument that falling into water would constitute an act of being shaken or slapped awake (like having a bucket of water thrown on you). So now it depends on the situation. Here is how I would handle it as a DM:

• If Randy is a PC, the act of falling in the water would wake him up. Why ruin a game session and the fun by killing a PC in such a cheesy fashion?
• If Randy is an NPC, it would depend on the feeling at the table. If the players, especially the player who is Margorie, acts like "meh, easy peasy" then Randy hitting the water will wake him up. A "meh" reaction means the encounter didn't have enough excitement too it. Waking Randy up will inject that excitement. However, if that spell was quick thinking by Margorie and/or the rest of the players are like "Whoah! She iced him like Han iced Greedo!" with the general mood of the players being excited and happy then Randy drowns.

When in doubt go with what is fun for everyone.

Answer 3

It’s impossible to have the body be in a state of sleep if it cannot breathe. The act of sleeping requires breathing albeit at a reduced rate. The moment breathing stops Randy is no longer sleeping but drowning without the benefit of holding their breath but conscious.

That moment for breathing to stop could take a round of sleeping in water before the first inhale of water.

• To add some verisimilitde: Sleeping Respiratory Rate of healthy adults in a relaxed state is about 12–20 times per minute. But in apnea cases can be one breath every 10 seconds. I include this because the magical slumber is a deep sleep.

  This is relevant because Margo may have another round before Randy wakes up to, perhaps, cast a Hold Person spell or grapple him so that he can’t stand up. This homebrew rule would mean a sleeping creature is considered to be holding their breath for 1 round.

When a creature runs out of breath, it can survive for a number of rounds equal to its Constitution modifier (minimum 1 round). At the start of its next turn, it drops to 0 hit points and is dying.

1. 1st round
   Randy attacks
   Margo casts sleep

2. 2nd round
   Randy is still exhaling in magical dreamland. (Holding Breath 1 round)
   Margo grapples him or casts Hold Person.

3. 3rd round Randy(CON 10)is conscious but out of breath and can attempt to escape grapple and then stand if successful.
   Since Hold Person saving throw happens at end of Randy’s turn it won’t help him because by the start of his 4th Turn he will drop to 0 hit points and is dying.

My question is why was Margorie the Mage bathing with her arcane focus or was there rose petals floating in the bath and she used them as her material component?