Can a Bag of Devouring empty an ocean?

Question

If you opened a Bag of Devouring underwater could it empty an ocean?

Answer 1

RAW No - because it won't consume water at all

A Bag of Devouring is a "a feeding orifice for a gigantic extradimensional creature". Logically speaking, a creature would have to be larger than the ocean itself to be able to consume such a volume of liquid.

However, there are no rules written for how the bag interacts with a substance such as water.

There are rules for

1. Animal or vegetable matter
2. Inanimate Objects

Water is not an object according to the game definition:

For the purpose of these rules, an object is a discrete, inanimate item like a window, door, sword, book, table, chair, or stone, not a building or a vehicle that is composed of many other objects.

Mainly, water is not discrete.

So according to the rules of D&D, if an object does not say it has an ability and a general rule also would not dictate that it does, the object cannot do that thing. So, since the Bag of Devouring is not listed as having the ability to process non-object non-creature entities, it does not have such an ability. Thus, it would not consume any water at all.

How should this be described in-game?

So if the ruling is that the bag will not consume water maybe simply say (after maybe a round or two of taking in water) that the bag's orifice has closed tightly shut as if it were the lips of some extradimensional creature that did not want to consume salt water.

Houserules to allow water consumption

If you wanted to allow this and make this work with the rules as written you could adapt the current rules to allow it to consume an amount of water comparable to the rates currently written in the rules.

Considering water an object (rule #2)

The easiest and most logical rule to adapt would be the object rule set (#2) since water would could be argued to be closest to an inanimate object than living things.

Using this ruling it would be able to consume 1 cubic foot of water per day which would be periodically ejected into a random plane. After consuming that much it would presumably refuse to take on any more water. Or you could make the bag / creature suffer an ill effect (stomach bursting, vomiting, etc.) after a few rounds of forced water consumption after this limit was reached.

Using creature consumption rules for water (rule #1)

The other method would be to try to fit water into the rule for devouring living things. Obviously water is not living, but this could be justified by saying that water is often consumed much as animal flesh and vegetable matter is. Thus the Bag of Devouring (and thus the extradimensional creature it is linked to) is literally drinking the ocean.

Using this rule, the bag could consume, at most, a volume equal to the largest creature size we have rules for (gargantuan) per turn.

Using the house rules, how long would it take?

Even if you ruled it capable of consuming water from an ocean, according to the rules given it looks like it is capable of handling 1 creature's worth of material every 6 seconds and/or a cubic foot of objects each day. It is going to take a LONG time to empty an ocean at that rate.

For example, the Pacific Ocean has an estimated volume of \$2.5\times10^{19} \text{ cubic feet} \$ of water.

Considering water an object (rule #2)

This case is very simple as it would take \$ 2.5\times10^{19} \text{ days}\$ (\$ 6.8\times10^{16} \text{ years}\$) to empty the ocean.

This an unfathomable amount of time. This is the longer of the two options.

Using creature consumption rules for water (rule #1)

So let's be super generous and allow the use of creature rules (#1) since it can consume one creature per round at best and this would allow for the absolute most material consumption according to the RAW.

If we assume this creature to be gargantuan that is \$8000 \text{ cubic feet} \$ in \$6 \text{ seconds} \$.

(This is also making the very generous assumption that a gargantuan creature occupies all of the 20x20x20 space it is said to control in the rules. This is highly unlikely.)

\$ \frac{8000 \text{ cu ft}}{6 \text{ seconds}} = 1333.3 \frac{\text{cu ft}}{\text{sec}} \times 60 \frac{\text{sec}}{\text{min}} \times 60 \frac{\text{min}}{\text{hour}} \times 24 \frac{\text{hours}}{\text{day}} = 1.1 \times 10^{8} \frac{\text{cu ft}}{\text{day}} \$

\$ \dfrac{2.5 \times 10^{19} \text{ cubic feet of ocean water}}{1.1 \times 10^8 \frac{\text{cu ft}}{\text{day}}} = \dfrac{2.1 \times 10^{11} \text{ days}}{ 365 \frac{\text{days}}{\text{year}}} = \text{ over } 575 \text{ million years} \$!

Hope your PCs are REALLY patient!

tl;dr RAW no, but if you want to houserule then it will still take a LONG time to empty an ocean using a Bag of Devouring