• Courtney Barkley

Diving Into Underwater Combat in Dungeons & Dragons


Combat in tabletop games can take place in a wide range of challenging terrains -- mountainsides, caves, even airships where you can easily plummet to your death. However, one location that pops up more often than you might expect is underwater.


While the fantasy worlds we play in vary widely, their geographical makeup is often based in large part on that of Earth’s, which means there’s a lot of water to go around. After all, 71% of the earth is covered in water, so similar Earth-like fantasy worlds are often just as blue. That means that as the Dungeon Master (we call them Quest Masters), you have to be prepared to run underwater combat.


Water: A Difficult Terrain

The first thing you need to keep in mind about water is that, for most races, it is difficult to move in. There are of course exceptions, everything from races to feats that allow you to move about easily in water, but for most player characters, maneuvering underwater is going to be a challenge.


In fifth edition, water qualifies as difficult terrain, meaning that players can only move at half movement. This can impede how they’re able to fight, and as the QM you can play up that difficulty. Describe how unwieldy and clumsy they feel in the water, how heavy their arms start to feel as they try to power through the water toward their foes.


In contrast, player characters who are able to swim easily can enjoy this time to shine! Their familiarity with the water can be a great aid to a struggling party.


Take a Deep Breath

Most player races can’t breathe underwater without some magical assistance. If your players don’t have a potion or spell that allows them to breathe underwater, they’re going to need to know how long they can hold their breath.


Thankfully, the formula is simple. 1+CON modifier tells you how many minutes they can hold their breath. After that, their CON modifier tells you how many rounds they can survive without drowning. At the start of their turn after that last round, their hit points drop to zero, and they cannot be healed or revived until they can take a breath.


Soggy Spellcasting

One way that some players may try to get around that movement hinderance is by hanging back and casting spells. While that may work in some cases, many spells are going to be difficult to pull off.


As you likely know, spells may require somatic (hand gestures), material (supplies), and verbal (speaking) components. While the first two can generally be handled underwater, the last one is a challenge -- one there’s been a lot of debate about in the D&D community.


The general consensus seems to be that if you can’t breathe underwater, your spellcasting will at the least be very limited, mostly to one spell before you’ve used up what air you have in your lungs and possibly start drowning. If you can breathe underwater, it gets more complicated. While D&D pros like Jeremy Crawford have claimed verbal spellcasting is doable in that situation, it really comes down to what you as the QM want to do. Decide ahead of time and be consistent with your players.


Also important to keep in mind in regards to spellcasting: any creature that is immersed in water is resistant to fire damage.


Waterlogged Weapons

Fortunately, when it comes to weapons, the underwater combat rules are laid out a lot more clearly. If you’re attempting a melee attack with anything other than a dagger, javelin, shortsword, spear, or trident, it’s going to be at disadvantage unless the character has a swimming speed.


For ranged weapon attacks, nothing beyond the normal attack range will hit. Attack rolls for crossbows, nets, and weapons thrown like javelins (like darts, spears, or tridents) will be normal, but everything else will be at disadvantage. When you’re facing off against enemies who can slip effortlessly through the water and bite or strike out with a tentacle without disadvantage, these changes can drastically increase the tension of an otherwise simple encounter.


Time to Dive In

As the QM, all of this is very easily explained by the fact that things move differently in water. There’s a lot more resistance, not to mention currents that move in ways the characters may be unable to anticipate. While this may be frustrating to your players at times, it can also help make the game much more memorable and immersive (pun fully intended).


Whether your players have taken a dive into the local coral reef or been transported to the water plane, you’re ready for them to encounter anything from a shark to a kraken with these water combat rules. Have you ever ran an underwater encounter in your game? Tell us about it below!

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