Clarifications on combat in water

Question

The rules in the DMG on water in different environments seem to contradict each other. The section on aquatic terrain claims that creatures at least chest deep in water gain improved cover from enemies on land. It also means, if my understanding is correct, that two chest deep creatures don't get improved cover against each other, but do against creatures on land. The Marsh Terrain section, on the other hand, says something similar (that water can be used to gain improved cover), but makes no mention of the enemy being in or out the water. But it adds that creatures with said improved cover take a -10 when attacking an enemy on land. Are these rules complementary, meaning that in any type of watery terrain improved cover granted by water applies only to attacks from the land, and that attacks from the water always take the -10 penalty against land, or do the rules actually change when in Marsh Terrain?

Also, related to the water rules: why does being underwater grant total cover, making most common attacks simply impossible from land, even for weapons like crossbows?

Regarding underwater targets and crossbows: because science! — SevenSidedDie, Jul 23 '14 at 04:41
@SevenSidedDie That means you should get penalties, not have it completely impossible. Clarity of the water would be a factor, of course. — Adeptus, Jul 23 '14 at 05:04
@Adeptus I don't disagree. But since that part of the question is "why?" and not "how should it be?": well, that's why. Also probably something about water resistance vs. melee weapons and projectiles, but I don't know the relevant science enough to judge the rules' faithfulness to it. — SevenSidedDie, Jul 23 '14 at 05:07

score 7 · Accepted Answer · answered Jul 23 '14 at 05:25

7

Because they are different.

Note, the water described in a marsh terrain is a "deep bog". The water described in aquatic terrain is just water. The environments are intended to be different and thus have different rules. The rules are not "complimentary" or additive.

Total cover for being underwater is somewhat of an oversimplification of refraction and the resistance provided by the water. I have hunted carp from the bank with a bow and, at least for me, it is largely blind luck determining where to aim. To be fair, on a sunny day, with clear water, with a fish very close to the surface, you can actually target them by shooting "beneath" them, if that makes any sense, but it is extremely difficult to know how much to correct for the refraction. Hence in the rules, it becomes "total cover". Add some turbidity and any significant distance from the surface or poor lighting and it effectively is total cover.

answered Jul 23 '14 at 05:25

Wyrmwood

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Those are interesting points. Could you elaborate on why you think the differences in environmments justify those specific differences? – derp Jul 23 '14 at 12:42
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That sounds like a better question for the designers, I just play here :-) – Wyrmwood Jul 23 '14 at 14:47
lol, that's true. Thanks for the answer, anyways! I'll wait a bit before choosing it, see if anything else comes out, but the help is always appreciated. :) – derp Jul 24 '14 at 00:46
If I was to hazard a guess, imagine dagoba from star wars or the hag's environment from Legend for a 'marsh' and any lake, pond or river for an 'aquatic' environment. In a marsh, there's not only very turbid water, but obstructions above water as well. – Wyrmwood Jul 26 '14 at 17:32

Clarifications on combat in water

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