I made a warlock that gains 40ft of swimming speed due to the fathomless pact (Gift of the Sea).

If I now pick the Gift of the Depths Eldritch Invocation will they add up and result in a swimming speed of 70ft?

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    \$\begingroup\$ I’ve added the [dnd-5e] tag, as the feature names (and their effects) are consistent with the 5e fathomless warlock and the eldritch invocation mentioned. Is this correct? \$\endgroup\$ Commented Sep 17, 2021 at 10:58
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    \$\begingroup\$ @PurpleMonkey Yes we can; experts who are able to pick up on critical contextual clues are able to discern that this is for D&D 5e; Matery in the future, please include a tag for the game system when you ask a question, as it avoids any potential confusion. Some games have similar terms or tools that may not be as clear, in terms of making a distinction between game systems, as this particular case was. \$\endgroup\$ Commented Sep 17, 2021 at 11:10

2 Answers 2


These features do not stack

Gift of the Sea states:

You gain a swimming speed of 40 feet, and you can breathe underwater.

Gift of the Depths states:

You can breathe underwater, and you gain a swimming speed equal to your walking speed. [...]

So while they do both grant you a swim speed, they would not add together because neither one says it increases your speed. When you have multiple speeds, moving using one deducts movement from the rest:

If you have more than one speed, such as your walking speed and a flying speed, you can switch back and forth between your speeds during your move. Whenever you switch, subtract the distance you've already moved from the new speed. The result determines how much farther you can move. If the result is 0 or less, you can't use the new speed during the current move.

Because of this, having multiple swim speeds doesn't cause them to add together. They would add together only if one of the features said it increased your swim speed. Two almost examples of the kind of wording you would need are the Goggles of Night which grant darkvision and increase the range if you already have it or the Monk's Unarmored Movement which increases any kind of speed:

While wearing these dark lenses, you have darkvision out to a range of 60 feet. If you already have darkvision, wearing the goggles increases its range by 60 feet.

Starting at 2nd level, your speed increases by 10 feet while you are not wearing armor or wielding a shield. [...]

  • \$\begingroup\$ I checked Tasha's, the abilities being asked about are for sure 5th edition D&D. Good answers. \$\endgroup\$ Commented Sep 17, 2021 at 11:07
  • \$\begingroup\$ The part about When you have multiple speeds, moving using one deducts movement from the rest is interesting, but IDK if relevant to answering what your swim speed is. The swimming speed equal to your walking speed straight up gives you one option for calculating your full swim speed. Using that swim speed doesn't involve any walking. The rule you quote is about e.g. walking to the edge of water and diving in, not about dealing with two swim speeds. It's not "because of this" rule that two ways of calculating your swim speed don't add, just like 2 ways of calculating AC don't add. \$\endgroup\$ Commented Sep 17, 2021 at 20:44
  • \$\begingroup\$ Although you do get the same result from considering yourself to have multiple swim speeds and applying that rule. It still seems a more complicated way to think about and explain it. I guess I should just post an answer with my explanation, although if you want to reword yours I'd be totally fine with that. \$\endgroup\$ Commented Sep 17, 2021 at 20:46
  • \$\begingroup\$ @Peter I couldn't find any rules saying you can't have multiple swim speeds. Thus, without the rule I quoted, they would actually stack additively because you could use one speed and then switch to the other \$\endgroup\$ Commented Sep 17, 2021 at 21:01
  • \$\begingroup\$ Ok, that's fair, that's an assumption I was making. I think it's justified (because it makes sense and gives the same result) so I'll go ahead and finish the answer I've been writing, and include a mention of the equivalence to your way of calculating. \$\endgroup\$ Commented Sep 17, 2021 at 21:04

They don't stack; neither one says "increase", instead they give you two different ways of calculating your swim speed. You get to pick the higher of the two.

It's exactly like with different ways of calculating your AC as a barbarian (wearing armor with its AC + dex, or using the unarmored defense class feature for 10 + dex + con. Not adding your con on top of leather+dex or breastplate+dex(max 2).)

Gift of the Sea states:
You gain a swimming speed of 40 feet, and you can breathe underwater.

Gift of the Depths states:
You can breathe underwater, and you gain a swimming speed equal to your walking speed.

"Gain a swimming speed" is phrased that way because most creatures don't have a "swim speed" to start with; in water they can move half their walk speed, and have certain disadvantages due to not having a swim speed at all. (Not as bad as how creatures without a fly speed do in the air, though. :P) Anyway, they don't mean "gain your walking speed as additional swim speed".

If they did, they'd have said so more clearly, like with Monk Unarmored Movement: your speed increases by 10 feet. This only adds to the speeds you already have, though; if you have a swim speed and/or fly speed, it adds to them. But if you don't, it doesn't give you a 10 ft fly speed. So the phrasing for a feature that gave you a swim speed if you didn't have one, or added to an existing one if you did, would have to make both those things clear. These just say "gain swim speed = x", so they're giving you options to set your swim speed, not add to it.

Medix2 points out that there don't seem to be rules against having 2 different swim speeds. You can calculate things that way and reach the same result, as explained in that answer, using rules intended for things like swimming to shore, standing up, and then walking.

Moving with one speed uses up that amount of movement from your other speeds, so there's never a way to do anything useful with your lower speeds of the same type. They might as well not exist, so following that logic always gives the same result as picking your best option for calculating a single swimming speed.

BTW, Gift of the Sea is faster for almost all creatures, unless you have something that increases your walking speed but not other speeds. Most features that increase speed don't limit it to one kind of speed. For example, Tabaxi is "double your speed" for a turn, barbarian and monk are "your speed increases".

Since very few creatures (and maybe no humanoid playable races) have a base walking speed >= 40 feet, a swim speed of 40 feet + any bonuses is always faster than a swim speed = walk speed (including bonuses).


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