D&D 5E Underwater Combat and Holding Breath - additional rule suggestions?

[Trit One-Ear]

Hey folks,
My party has begun a island-hopping nautical chapter in our adventures, and in prep I've been planning additional/circumstantial rules that I may not have regularly used before. One such rule/rule set is Underwater Combat.
I've reread the relevant sections in the PHB, and done some extra reading online and generally, the opinion I find is that there aren't enough RAW to make holding your breath a real factor in combats. I've seen suggestions for adding mechanics to help with this and read up on a variety of approaches.

My biggest complaint with RAW is that for any given fight, most time being grappled underwater (for example) is effectively the same as being grappled on dry land. Yes, you can design encounters that add additional obstacles or hazards to increase the risk of running out of air. Yes, you can rule that a creature surprised and pulled underwater doesn't have a full breath of air... but that feels too punishing to me. It should be enough to throw an aquatic monster at a party and have the risk of being held underwater heighten the stakes without having to do a lot of extra work.

I'm currently thinking of a system that uses the RAW for underwater exploration, but in the chaos of combat reduces the number of round creatures can hold their breaths (still utilizing Con mod), and then having actions like casting spells with verbal components and taking damage lower that number over time... but I don't want to reinvent the wheel if I don't have to.

My question for you all: Have you tried any additional breath-holding mechanics (including interactions for casting spells and taking damage), and do you have any advice based on your experiences?

 

[Flamestrike]

Technically, the way the rules work RAW, as soon as an underwater caster casts a spell with V components, they are no longer holding their breath, start suffocating, and after a number of rounds equal to Con mod (minimum of 1) drop to Zero HP (and dying).


I altered it so a Creature can hold its breath for (Con) in rounds (so a minute for your average human). A creature proficient in Athletics doubles this number. On the start of each of your turns after that, you must attempt a Con save, or drop to Zero HP and start to drown. The DC is 5 (+2 for every round past the first save).

Casting a spell with a V component uses up 5 rounds of air.

 

[Urriak Uruk]

Check out this episode of Critical Role... Mercer uses much of the ideas you have mentioned here for the underwater combat. Including things like spells hastening how quickly someone drowns.

 

[commandercrud]

The underwater rules for 5e are utterly absurd.

 

[Vaalingrade]

The underwater rules for 5e are utterly absurd.

Probably to try and rectify the fact that players generally hate underwater adventuring.

 

[Stalker0]

An interesting idea would be the countdown variant from level up.

at the start of every turn, roll like 10d6, and remove any dice that shows a 5 or 6. If you take an action that consumes air (like fighting), roll another check immediately. Something that involves talking auto removed a die.

when the die runs out, you are out of air.

that gives it a nice random component to make things more interesting

 

[Trit One-Ear]

Check out this episode of Critical Role... Mercer uses much of the ideas you have mentioned here for the underwater combat. Including things like spells hastening how quickly someone drowns.

This is actually what really got me thinking about this recently. I'm making my way through CR for the first time, and watched this a few weeks ago, and really liked how Mercer made underwater encounters feel more dynamic. I should give it a rewatch though and see if I can't codify his approach.

 

[Urriak Uruk]

This is actually what really got me thinking about this recently. I'm making my way through CR for the first time, and watched this a few weeks ago, and really liked how Mercer made underwater encounters feel more dynamic. I should give it a rewatch though and see if I can't codify his approach.

Yeah I coincidentally just finished this episode last week! The underwater fight I don't think is too long, so it's probably worth a listen to hear what is used, and maybe tune it a little better for usage. Taking damage and using spells seem to be what hastens drowning, not sure what else.

Also, you might want to tweak it so that when your drowning, you don't drop to 0 hp but are just unconscious (and making death saves) instead. But if you are taken out of the water, you still have the same hp.

 

[Charlaquin]

I just rule that holding one’s breath requires concentration. That way the grappler can attack the creature they’re trying to drown to try and force a concentration save.

 

[Flamestrike]

Check out this episode of Critical Role... Mercer uses much of the ideas you have mentioned here for the underwater combat. Including things like spells hastening how quickly someone drowns.

Casting a spell with V components already does this. As soon as you do so, you drown (zero HP) Con mod rounds (minimum of 1 round) later.