Is it possible to use the Shape Water spell to control the water generated by the Tidal Wave spell?

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    \$\begingroup\$ Please note for future reference, while brevity is acceptable, details and context are much more useful (in terms of both questions and answers) for both you and the community. Consider including things like why you're confused about a specific topic (are the rules ambiguous? has a DM or player said something that you're not sure about? etc.) or the specific situation that lead you to ask the question. That way we've got more details to work with and can better tailor answers to your specific needs. \$\endgroup\$ Sep 3, 2019 at 23:19

3 Answers 3


The tidal wave spell has a duration of instantaneous, and ends with this sentence:

The water then spreads out across the ground in all directions, extinguishing unprotected flames in its area and within 30 feet of it, and then it vanishes.

So no, you can't use shape water on the water from tidal wave, because there is no point in time where that's possible. Even if you readied an action to do it, reactions take place after their triggers, so the water will still be gone at the point when you cast shape water.

  • \$\begingroup\$ And even if you could, the water would presumably just disappear immediately afterward anyway. \$\endgroup\$ Sep 4, 2019 at 0:14
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    \$\begingroup\$ You wouldn't set the trigger "when tidal wave is cast", you would set the trigger "When water appears" or, if you must "When water crashes down on X area". While the duration is instantaneous, there is a sequence of events outlined and there's no reason to think that just because no time is passing one cannot come after one thing and before another-- if they were truly simultaneous the caster of Tidal Wave could pick the order the steps happened in and that is clearly not the way the text reads. \$\endgroup\$ Sep 4, 2019 at 2:03
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    \$\begingroup\$ @thedarkwanderer "Many spells are instantaneous. The spell harms, heals, creates, or alters a creature or an object in a way that can't be dispelled, because its magic exists only for an instant." If it's impossible to cast Dispel Magic on the water, there's no reason to assume it's possible to cast other spells on the water. \$\endgroup\$
    – Miniman
    Sep 4, 2019 at 2:11
  • \$\begingroup\$ Let us continue this discussion in chat. \$\endgroup\$ Sep 4, 2019 at 5:18

Rule as written, it seems difficult

As Miniman already stated, the effect of Tidal Wave is Instantaneous and the water vanish at its end. Shape Water having a casting time of an Action, only a Ready action could allow to use it in this case.

I said "could" because the choice of the trigger for the Ready action seems difficult :

  • If you choose "when X is casting Tidal Wave", the trigger would be the same as a counterspell : the spell wouldn't be cast yet and there would be no water to shape.

  • If you choose "when Tidal Wave is cast", you would cast your spell after the trigger happened and, since Tidal Wave is instantaneous, the spell effect would already have resulted and the water vanished.

  • A dark wanderer under another response suggest "when water appear", stating that there is a sequence of event in the spell description. I guess this is technically possible but even if the DM allow it, the effect would be minimal : the sequence is "water appear doing damage" then "water vanish" so you would be able to manipulate the water only after the damage done.


As a DM, I would certainly allow it to reduce the damages with a contest of spellcasting check against the caster.



Shape Water does not require the water it affects to be non-magical. While it would require a readied action, casting Shape Water on the water created by a Tidal Wave spell is not only possible but also would allow you potentially protect some unprotected flames from being extinguished by ensuring they were not within 30' of the water created by the spell, since in is, in fact, that water's area and not the spell's which determines the radius unprotected flames are extinguished in.

Note, however, that the actual damage the spell deals is completely disconnected from the water it creates and so, while you could absolutely avoid getting hit by the water from the spell with a well-timed freeze or flow-reversal or whatnot depending on environmental circumstances you would still be subjected to the massive bludgeoning damage from the spell since, again, that has nothing to do with being hit by the water under the text of the rules. You may well be able to argue that preventing the water from hitting you should prevent the damage, however, depending on the style of your DM.

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    \$\begingroup\$ There's a point on which I'm not sure I agree, "you would still be subjected to the damage": the spell states "You conjure up a wave of water that crashes down on an area within range..[...]. Each creature in that area must make a Dexterity saving throw." but if you redirect it with Shape Water, it no longer crashes down on the area it otherwise would have, so you wouldn't be considered "a creature in the area the water crashed down in" and wouldn't have to take damage from it. \$\endgroup\$ Sep 3, 2019 at 22:52
  • \$\begingroup\$ The sentence you elipse clarifies that: "The area can be up to 30 feet long, up to 10 feet wide, and up to 10 feet tall. Each creature in that area must make a Dexterity saving throw." Now, the disjunction between water hitting and damage is definitely not something I'd consider intended by the spell, and so I would rule that blocking the water from hitting you e.g. via the Shape Water cantrip is sufficient to also avoid damage from the spell. But that would be a ruling contrary to the text, not one interpreting it. \$\endgroup\$ Sep 3, 2019 at 23:28
  • \$\begingroup\$ Basically "a creature in the area the water crashed down in" isn't a reasonable interpretation of "that area" since that area was just defined as a region of space and the text merely states that water crashes down into the area you choose. Even if water no longer crashes down it still was part of the area you chose, and that, not that+water, is what triggers rolls for damage. \$\endgroup\$ Sep 3, 2019 at 23:30
  • \$\begingroup\$ That is a fair point. I'm with you on probably ruling that the damage would be avoided, but I concur with your assertion that the rules as written would say otherwise. \$\endgroup\$ Sep 3, 2019 at 23:41

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