The Underwater Combat rules on attacking state:

When making a melee weapon attack, a creature that doesn't have a swimming speed (either natural or granted by magic) has disadvantage on the attack roll unless the weapon is a dagger, javelin, shortsword, spear, or trident.

A ranged weapon attack automatically misses a target beyond the weapon's normal range. Even against a target within normal range, the attack roll has disadvantage unless the weapon is a crossbow, a net, or a weapon that is thrown like a javelin (including a spear, trident, or dart).

When it says underwater combat, I assume this is true while both that attacker and target are underwater, but the rule doesn't seem to explicitly define whether this rule is triggered when:

  1. Both are underwater
  2. Attacker is underwater, target is on land
  3. Target is underwater, attacker is on land

Scenario 1 obviously follows the underwater combat rules, but how about 2 and 3? Do both of them follow the underwater combat rules?


The sentence immediately proceeding the quote in the question states (PHB p.198):

Underwater the following rules apply.

This does not say who is underwater, just that the combat is in some way underwater. The most straightforward and obvious way to interpret and play this would be to apply the rules as written when either party is underwater, unless the DM's common sense says otherwise (e.g. the target is only 1" under the surface of the water) or there is an explicit rule that states otherwise (e.g. the Wall of Water spell XGTE p.170).


You should use realistic logic plus the rules

I don't have the rulebooks, so I'll only state with what you wrote here. If you think to these situations with this world logic, you should get something like that:

  1. Both are underwater: As you said, the rule states that they both have to apply the underwater rules.

  2. Attacker is underwater, target is on land: Here, I would say that the attacker has the disadvantage of underwater combat. Imagine it, if something is underwater and tries to target anything - either something underwater as well or even something out of the water - it'll have the same restrictions as it's in the same situation (underwater). It's the fact that water restrains the attacker's movements (or lowers a ranged weapon's range as stated in the rule) that causes disadvantage, not the actual fact that the attacker or target is underwater (plus trying to aim at an out-of-water target would be even more difficult if the attacker has their head underwater due to the liquid surface's visual disturbance).

  3. Target is underwater, attacker is on land: Here, it depends on where exactly the target is. If it's at the surface, I would assume that the attacker doesn't have any disadvantage due to the fact the attack doesn't have to "touch" the water at any moment. But if the target's completely underwater, the attacker may have to go himself a bit underwater to reach the target if they aren't using a ranged weapon (maybe only their arm to get in range), and disadvantage should be attributed depending on the "percentage" of the attacker's body that has to be underwater. For ranged weapons which may have disadvantage underwater (i.e. a simple bow), you should also attribute disadvantage based on the distance the projectile has to go through the water before hitting the target.

As a summary, I would that it's the DM's job to impose or not impose the disadvantages of the underwater combat, keeping in mind that it's the attack moving through the water which imposes these disadvantages, not the fact of one creature or the other being underwater.

  • 2
    \$\begingroup\$ So a few points 1) we expect answers to be supported. Do you have any experience using this type of ruling? If so, how did it turn out? 2) Using logic is not always going to be the best. Since D&D is a game and not a simulation, oftentimes it has to break logic to be fun. Without some other sort of backing there is no way to tell if your rulings would be fun, tedious, or break something else in the game. \$\endgroup\$ – Rubiksmoose Feb 8 at 15:09
  • \$\begingroup\$ @Rubiksmoose actually I never player played a game of D&D (even if I would love to try this RP) so I can't bring experience here, I just wanted to help the OP telling him how I would handle it as a DM. I'll try to give more attention to the experience point in my next answers, sorry. \$\endgroup\$ – Zoma Feb 11 at 6:37

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