I had a player fighting against sahuagin by the shore the other day and he was dropped to 0 and dying. Because of his location, though, he landed in shallow water (2-3′ deep) which I ruled was enough to drown in.
The rules for suffocation (PHB pg. 183) are specific to state:
A creature can hold its breath for a number of minutes equal to 1 + its Constitution modifier (minimum of 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.
I was having difficulty adjudicating this because the character was already at 0 and now was just inhaling water.
In this scenario, does the character just make death saves as normal, or would they automatically fail them?
FYI, I ruled that he would auto-fail the saves since he’s just inhaling salt water now and takes a level of exhaustion, but if the rules have something specific for this, it’d be helpful to know.
In my PHB the full suffocation rule is (emphasis mine):
A creature can hold its breath for a number of minutes equal to 1 + its Constitution modifier (minimum of 30 seconds).
When a creature runs out of breath or is choking, 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, and it can’t regain hit points or be stabilized until it can breathe again.
For example, a creature with a Constitution of 14 can hold its breath for 3 minutes. If it starts suffocating, it has 2 rounds to reach air before it drops to 0 hit points
This is my RAI interpretation of your situation:
The character is unconscious and dying from damage, and begins making death saving throws immediately
The character cannot voluntarily hold their breath, so the minutes are not applicable here – the rounds before the dying effect of suffocation begin immediately
If the suffocation effect’s rounds elapse, then the character cannot regain HP or be stabilized until they can breathe, and are dying from suffocation (and possibly damage as well, but there is no RAW precedent for stacking these)
That large, bolded part of the rule is the most important aspect of this situation. If a druid casts healing word on a character before suffocation’s dying effect kicks in, they’re back in the fight. If not, healing word fails to revive them – someone must help them breathe first.