Rewriting Control Water's whirlpool option

Question

One of my players recently got access to the control water spell, and in the last session, had the opportunity to use the Whirlpool option for the first time. It went badly! This spell is so poorly written that it brought the game to a screeching halt while the player and I tried to figure out what exactly the whirlpool does.

If you're interested in our problems, consider the following questions: Under what circumstances does a creature need to roll an Athletics check to 'swim away', other than using an action to stop being trapped in the vortex? What does it mean for a creature to be caught in the vortex "until the spell ends" but then make a save at the start of each of its turns where success means it "isn't caught"? What is the game effect of being "caught"? I also had difficulty adjudicating the shape of the whirlpool on a map. (I'm not particularly interested in excessive discussion of the answers to these questions; even if I make a ruling, I feel the spell is badly written enough that it will continue to cause problems and confusion.)

I made a ruling just to get through that combat, but afterward my player voiced concerns about using this spell in the future, both that the mechanics were convoluted and that the effect was ultimately unimpressive given that it costs a 4th level spell slot. While it seemed like a good choice for an adventure that features many underwater foes, it was a disappointing result.

So that's what prompted to examine this spell and try to come up with a homebrewed version that is quick to apply at the table and has an effect that's worth the cost of casting. I'm hoping to get an idea of whether my proposed rewrite is a viable replacement for the Whirlpool option of control water, while changing nothing else about the spell.

Whirlpool. A vortex forms in a cylinder 25 feet tall with a radius of up to 25 feet, centered on a point you choose within range. This effect requires a body of water large enough to contain the entire cylinder. The vortex is difficult terrain, and is surrounded by a zone of suction that extends a further 25 feet.

When a creature starts its turn in the water within the vortex or the zone of suction, it must make a Strength saving throw (or choose to automatically fail). On a failure, it is pulled 10 feet towards the center of the vortex (provided there is an unoccupied space to do so) and becomes unable to move further away from it until the start of its next turn. Then, if the creature is within the vortex, it takes 2d8 bludgeoning damage if it failed the save, or half as much if it succeeded.

At the start of your turn, unattended objects that are not secured are moved and damaged as if they had failed the saving throw.

As an action, a creature that failed the saving throw can make a Strength (Athletics) check against your spell save DC. A creature in the vortex takes disadvantage on this check. On a success, the creature can move away from the vortex.

I think this compares favorably to other spells of the similar level, like Evard's black tentacles, sleet storm, and ice storm, with a huge area and moderate crowd control. Does this seem balanced? Are there any problems with the wording or rules interactions?

Answer 1

Seems balanced

This version seems to be pretty close to the original function of the whirlpool option, so I would not expect balance issues. The spell already is quite situational, requiring a large body of water to work, so even if it were a bit unbalanced, unless you are playing a water-based campaign, it is not going to be an issue; you need to prepare it for the perfect situation, otherwise you will have wasted a preparation slot.

If anything, I think this version may be weaker than the original, as creatures in the suction area may not need to use an action on a Strength (Athletics) check to escape the pull. I may have a blind spot here, but I do not really see how this changes the damage output materially, if what you were concerned with was what you saw as underwhelming damage.

While I do not see a balance issue, I'm not sure this version is less work:

• I think it is a plus for flavor that creatures continue to be pulled towards the center once inside the vortex. In the original text, this was not the case, the creature just took damage once inside. It however does make the administration in game more time consuming, as you have to continue tracking movement. The term caught is used in the original to imply creatures cannot leave the area of the vortex, but lacks guidance on if they can or cannot move within. This avoids using the restrained condition, as it has additional functional impact like giving advantage/disadvantage to attacks, but is less clear.

• Creatures are forced to make a save in this version. Why? Shouldn't a creature that is not expending effort to escape the suction of the vortex automatically be pulled in, like an object? Conversely, shouldn't a creature trying to avoid being sucked need to expend effort to avoid the effect, like they need to get out of it? This also might create more admin work for the DM, as now you need to roll saves for everyone in addition to rolling athletics checks for those that want to get away.

• This version does not use the "if a creature first enters the area or starts its turn there" wording that is used in nearly all spells of this kind for describing when the save and damage happens. I think it would be better to remain consistent with that template, which is well understood e.g.:

Web: Each creature that starts its turn in the webs or that enters them during its turn must make a Dexterity saving throw. On a failed save, the creature is restrained

Spirit Guardians: when the creature enters the area for the first time on a turn or starts its turn there, it must make a Wisdom saving throw. On a failed save, the creature takes 3d8 radiant damage

Sleet Storm: When a creature enters the spell's area for the first time on a turn or starts its turn there, it must make a Dexterity saving throw. On a failed save, it falls prone.

Black Tentacles: When a creature enters the affected area for the first time on a turn or starts its turn there, the creature must succeed on a Dexterity saving throw or take 3d6 bludgeoning damage and be restrained

Control Water: When a creature enters the vortex for the first time on a turn or starts its turn there, it must make a Strength saving throw. On a failed save, the creature takes 2d8 bludgeoning damage

Damage output of the original

Comparing whirlpool to black tentacles, which is probably the fairest comparison as both are 4th level:

• The tentacles' duration is 10 times shorter at one minute vs ten. This will rarely matter for combats, as combat tends to be resolved in 4-5 rounds, but may have non-combat applications like covering an escape
• The expected initial damage of both is comparable at about 7 points, as tentacles deals no damage on a save (both Dex and Str save fail rates up to CR 10 are around 60%)
• Once failed, tentacles deals auto-damage, which will be 10-11 points, and it imposes the restrained condition - this is stronger than whirlpool by 50% for raw damage.
• The area of tentacles however is much smaller (20 feet square or 400 square feet, vs nearly 2,000 square feet of vortex and over 7,800 feet overall affected area. This means you can potentially hit five times as many creatures and deal much more damage overall with control water.

Control water has no power issue, its issue is that it is situational and the wording is a bit vague. When you can use it, it should hold its own vs other 4th level spells. You can also use it to part water and expose underwater creatures on dry ground in cave lakes, or to capsize enemy vessels, so in the right circumstances other modes can be very effective, too.