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

[iserith]

In my games, you can't cast spells with a V component underwater unless you can breathe water.

In D&D 4e, there were a couple notable rules that made things interesting. First, many creatures had an Aquatic trait, which basically meant that it had combat advantage against creatures that didn't have the Aquatic trait (if I remember correctly). You could make this a trait in a D&D 5e monster's stat block easily enough: "While swimming, the [monster] has advantage on attack rolls against creatures in the water that do not have a swim speed."

As well, in D&D 4e, if holding one's breath in combat, the player had to make a DC 20 Endurance check at the end of the character's turn in which the character takes damage. Failing the check meant losing a healing surge and had to make subsequent checks each round at +5 DC each. If the check was failed and the character has no healing surges left, the character takes damage equal to his or her level, even after being reduced to 0 hit points (until death).

This latter rule's a bit fiddly by D&D 5e standards in my view, but it seems like something easy enough to adapt. Maybe something like damage forces a Constitution check with failure reducing the time the character can hold its breath by 1 minute.

 

[Asisreo]

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?

I've made a houserule before that getting hit requires a DC 10 constitution save to prevent going from holding breath to suffocating. It didn't go over well so I scrapped it but if you're players are tolerant with the idea of the casters drowning easily, it might be something to look into.

Nowadays, I just use RAW to make swimming sections dramatic, but in ways that are a bit more...interesting.

Let's say a player has a Con 14 (+2) meaning they can hold their breath for 3 minutes. While swimming, they can move 150ft/min or 200ft/min if moving fast. If I had a swimming section that stretched to 600ft (or 300ft down and up), the player would be incentivized to swim at a fast pace the entire time. Now, every round the player takes fighting is another round where they tick one round closer to death before the swim back up.

In practical terms, as a DM, you can track how many rounds the player has been in combat, then place them that many rounds of movement under the water. That way, they still have a chance by using a Dash action but if they stayed under for too long, they'll actually drown.

You must make this apparent ahead of time, though. Telling them each round in underwater combat counts against their breath time is important both for tension and to let them know the quicker they can stop or avoid combat, the better.

 

[Quickleaf]

Yeah, my approach is pretty simple.

If you enter the water while you can't take a reaction (e.g. already used your reaction, surprised, incapacitated due to paralyzation/stunned/unconscious), then you don't have time to take a gulp of air. You immediately start drowning, i.e. you have rounds not minutes.

Otherwise you can use your reaction to gulp air, and now have minutes to survive underwater.

If you take damage while holding your breath, you reduce the number of seconds remaining on your held breath by the damage you took.

Optionally, any non-magical self-healing powers, such as the fighter's Second Wind or monk's Quickened Healing also add seconds equal to the amount healed back to your held breath.

 

[Trit One-Ear]

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

Everyone hates the underwater level.

 

[Trit One-Ear]

I've made a houserule before that getting hit requires a DC 10 constitution save to prevent going from holding breath to suffocating. It didn't go over well so I scrapped it but if you're players are tolerant with the idea of the casters drowning easily, it might be something to look into.

Nowadays, I just use RAW to make swimming sections dramatic, but in ways that are a bit more...interesting.

Let's say a player has a Con 14 (+2) meaning they can hold their breath for 3 minutes. While swimming, they can move 150ft/min or 200ft/min if moving fast. If I had a swimming section that stretched to 600ft (or 300ft down and up), the player would be incentivized to swim at a fast pace the entire time. Now, every round the player takes fighting is another round where they tick one round closer to death before the swim back up.

In practical terms, as a DM, you can track how many rounds the player has been in combat, then place them that many rounds of movement under the water. That way, they still have a chance by using a Dash action but if they stayed under for too long, they'll actually drown.

You must make this apparent ahead of time, though. Telling them each round in underwater combat counts against their breath time is important both for tension and to let them know the quicker they can stop or avoid combat, the better.

I like your approach for making RAW more exciting, and think that it's a great example of good DMing in 5e. It does highlight one of my problems with the rules as they stand though - as a DM you really have to tailor your encounters to make holding your breath even relevant.

My ultimate goal is to make it feel different being grappled underwater than on land. In a fight without a lot of pre-thought and set up someone is grabbed and pulled underewater, RAW holding your breath isn't likely to be a factor at all. Most PC's will be able to get free long before their breath runs out. I want to make even a simple fight (say, if someone gets pulled off a ship and grappled by an aquatic foe) feel different and dynamic.

 

[jayoungr]

My ultimate goal is to make it feel different being grappled underwater than on land. In a fight without a lot of pre-thought and set up someone is grabbed and pulled underewater, RAW holding your breath isn't likely to be a factor at all. Most PC's will be able to get free long before their breath runs out. I want to make even a simple fight (say, if someone gets pulled off a ship and grappled by an aquatic foe) feel different and dynamic.

In what ways do you want it to be different? Is concern about drowning the main thing you want the fight to have? That's what most of the answers in this thread have focused on (probably due to the thread title), but maybe you are looking for some other flavor differences as well?

 

[Oofta]

A lot of good suggestions. Another thought I've had is to use exhaustion for running out of breath. After a number of rounds equal to your con, make a con save or you gain a level of exhaustion.

Unlike normal exhaustion you regain a level of exhaustion for every round you can breath normally. So if you are in stage 3 of exhaustion (Disadvantage on attack rolls and saving throws) and get a single gasp of air you improve (to speed halved). At stage 6 you are unconscious and dying (no magic healing), make death saves.

So if you were at stage 6 but not dead and can breath normally you go back to normal after 6 rounds.

 

[Trit One-Ear]

In what ways do you want it to be different? Is concern about drowning the main thing you want the fight to have? That's what most of the answers in this thread have focused on (probably due to the thread title), but maybe you are looking for some other flavor differences as well?

No, I think the suggestions here offer a variety of approaches to get what I'm hoping for which is, as you said, making the drowning an actual concern in combat. I think it will take some playtesting to find the right balance between it being inconsequential or it being too punishing. I'll tinker around a bit and post what I come up with!

 

[jayoungr]

As it happens, I'm expecting to run some underwater combat soon myself, so I'd be very interested to see what you come up with.

 

[Trit One-Ear]

Here we are! I've drafted up a version of what I'm currently playtesting to see if this rule set accomplishes my desire to make the threat of drowning in combat present without being overwhelming.

After rewatching the Critical Role episode linked above, I realized there were some things Matt did that I appreciated as a DM, but don't seem to help in creating a consistent ruleset. Mainly, he appears to have some internal tally going for the party, and is not very transparent about the number of rounds characters will be able to hold their breath. This creates a situation in which, as a DM, he is able to raise the tension as he sees opportunity, but his players don't have a clear sense of the immediateness of the threat of drowning. Personally, I know my players would hate that, so I've done my best to codify a system that is clear to both players and DM and allows for some of the exciting moments that occur in that episode as inspiration.

Here is my current draft of Underwater Combat Rules.

I ran a combat with my group last night, during which I hoped to test these rules. The PCs and their crew were dragged off the ship and into the waters, and I was just about to explain my new Breath rules... when the cleric cast Water Walk. A few creatures still had to escape the grappling spirits below them, but once they did they quickly popped to the surface.
So! These rules are, as of now, effectively untested, but please feel free to use them as you wish!

Also, any additional comments or notes are, of course, welcome.