# Is your movement penalized underwater if you have a swimming speed but choose not to use it?

Here are the rules on underwater movement:

While climbing or swimming, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a climbing or swimming speed.

I have a question related to the highlighted passage: if a creature has a swimming speed, but chooses not to use it, would their movement be penalized as per the above rules, or would they get the same benefit [no speed reduction] that creatures using their swimming speed have?

One case where this would be useful is if a character has a walking speed of 50 feet and a swim speed of 30 feet. Since the character has a swim speed, can it use its walking speed to move faster (since it no longer has to spend extra movement)?

# Yes, if you don't use your swim speed then your movement is penalized

Swim Speed is not a generic rule that allows you to use your standard movement speed for Swimming, it's a specific movement rate when Swimming. All creatures that have a Swim Speed have one listed at a specific value. It's not a generic ability that enables them to use their standard speed for swimming, but a specific and different value from the other movement speeds.

Because we are talking about specific speed values, the logic here is fairly simple based on the rules regarding Swimming. WoTC released an errata that clarifies this:

Each foot of movement costs 1 extra foot (2 extra feet in difficult terrain) when you’re climbing, swimming, or crawling. You ignore this extra cost if you have a climbing speed and use it to climb or a swimming speed and use it to swim.

This now clearly gives you the option of using your swim speed and ignoring the extra cost, or using your regular speed with the penalty.

• Could you explain the logic that led you to state you automatically use your swim speed while underwater (or quote the relevant text) Commented Jul 5, 2018 at 18:31
• Please clarify how it is that you think the RAW logic says that. Bonus points for providing understanding of what you see as the flaws in interpretation by Blake Steel's answer. ...or is there some other pertinent rules text that we're missing? Commented Jul 5, 2018 at 18:32
• @BenBarden I've submitted additional information and an example of why it doesn't make sense to allow Swim speed to be whatever your highest current speed is. Commented Jul 5, 2018 at 18:53
• The rules do NOT say specifically that you lose access to using your other speeds, only that running out of using your 'new' speed (Swimming) means you can't use any more of that speed, not that the other speeds you possess are unavailable, including your standard movement, which would be penalized 50% to continue your move.
– user47897
Commented Oct 25, 2018 at 21:43
• You may want to update with regards to the new PHB errata Commented Nov 16, 2018 at 20:10

RAW, the creature can move its full walking speed

While climbing or swimming, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a climbing or swimming speed.

This implies that you need not use your swimming speed, merely have it. (Also, amusingly, it was pointed out that this also means that a creature with a swim speed can climb at full speed and vice versa)

However, I suspect RAI is:

While climbing or swimming, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature is using its climbing or swimming speed, respectively.

• Trying to intuit RAI is... treacherous. Commented Jul 5, 2018 at 18:15
• I'm not sure that the use of "has a" makes it a choice. Commented Jul 5, 2018 at 18:20
• @BenBarden if the RAW interpretation is correct, the actual swim speed matters not. All that would matter is the binary of "swim speed" or "nah" Commented Jul 5, 2018 at 18:21
• I was under the impression (and I think this is what NautArch was getting at), was that the listed speeds are the speeds you use in those modes. That is, your swim speed is not "a speed that you can use while swimming", it is "your speed when swimming". The half movement rules are just ways to calculate a swim speed for creatures that don't have one listed. Commented Jul 5, 2018 at 18:42
• @Blake Steel ...or have a climb speed. It's a bit silly, but it's there. Climb speeds help you sim better. Commented Jul 5, 2018 at 18:52

The "or" can be confusing here. Best to break this into two separate rulings that essentially say the same thing.

While climbing, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a climbing speed.

While swimming, each foot of movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a swimming speed.

When listed, climbing and swimming speeds are always preferable to walking speed halved so it is irrelevant which one a character would choose. They should always choose the climbing or swimming speed unless they had a ring of free action where it may be preferable to choose walking speed instead.

• Consider a situation where you have a 30ft walking speed and a 10ft climbing speed. Could you climb the whole 30ft at regular speed because the "creature has a climbing speed" statement is true? Commented Nov 13, 2020 at 16:07
• It would be halved so they would climb at 15. You would not normally see a listing for walk 30 and climb 10 however. It is would normally be climb 20+. They are still eligible to use walking speed, however they would be subject to ability checks where there is a chance of falling. Commented Nov 16, 2020 at 5:23
• The errata mentioned above clarifies the rule just fine in my opinion. Commented Nov 16, 2020 at 5:36
• I agree that the errata covers it, but you don't mention it in your answer. An answer should stand on its own, not rely on information given in another answer. My query was mostly based on the statement "climbing and swimming speeds are always preferable to walking speed halved so it is irrelevant which one a character would choose". While this may be the case currently (I haven't gone through all monsters to check), that does not mean this will always be the case. Commented Nov 16, 2020 at 16:00

## You end up splitting the difference.

You can move faster than your swim speed suggests, but not your full regular speed. Once you use up all the movement your swim speed grants, you can just switch speeds:

If you have more than one speed, such as your walking speed and flying speed, you can switch back and forth between your speeds during your move. Whenever you switch, subtract the distance you're already moved from your 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. (PHB p. 190)

You've moved 30 ft swimming, so you subtract that from your new (regular) speed of 50 ft. That leaves 20 ft of movement. Using it costs double, because you're using it to swim, but it's enough for an extra 10 feet of movement.

Naturally, this will only work if your regular speed is faster than your swim speed.