The companion piece. If you want the rules, the four effects, the full edition history, and the 2014 versus 2024 breakdown, that’s all in the Control Water explainer post. Go read that first, then come back, because this is where we talk about actually pointing this spell at a ship and pulling the trigger.
Control Water is a spell with a split personality. Most of the time it’s a quiet utility pick, and then the party steps onto a boat and it becomes the single scariest thing at the table. I’ll be straight with you up front: the Reddit well on this one is shallow. Unlike a chaos spell like Catapult, Control Water has really only two on-topic threads with any meat on them, and one of them is a 380-comment war about ships that carries almost the whole conversation. So a lot of what follows is built straight from the rules text, and I’ll tell you plainly which is which. When an idea comes from a thread, I cite it. When it comes from the spell itself, I say so. No invented links here.
I sorted it into four buckets. Real uses that lean on the actual rules. Cheeses that are clever and mostly legal. Questionable stuff that lives or dies by your DM. And the deviant stuff, because even a utility spell attracts weirdos. Fight me in the comments, but bring receipts.
REAL USES (rules-solid, straight from the text)
1. Part the water and walk across. The signature move, and it’s just the Part Water effect doing its job. You open a 100-foot-wide trench with walls of water on both sides and march the whole party across a river, a moat, or a flooded passage on dry ground. Hold concentration and the corridor stays open. This is pure RAW, no DM permission needed. (Rules-derived, Control Water Part Water effect, PHB p227.)
2. Drain a flooded room to find what’s underneath. Redirect Flow reroutes moving water anywhere you like, even up walls and over obstacles. Point a flooded dungeon chamber’s water out a doorway or down a shaft and you can empty a room to reach a sunken door, a drowned lever, or whatever the last party dropped down there. (Rules-derived, Redirect Flow effect.)
3. Reroute a river to cut off or drain something. Same effect, bigger canvas. A river feeding a moat, a mill, or an enemy camp can be shoved somewhere else for ten minutes. Drain the moat before you assault the keep, or starve a waterwheel that’s powering something you’d rather turn off. Rerouting water is one of the oldest siege tricks in the book and this spell just does it. (Rules-derived, Redirect Flow effect.)
4. Flood the shore to bog down an advancing army. The Flood effect raises standing water up to 20 feet, and if there’s a shoreline in your cube, that water spills onto dry land. Turn a beach or a riverbank into difficult, thigh-deep muck right as the enemy tries to cross it. (Rules-derived, Flood effect. Note the 2024 printing trimmed the explicit shore-spill sentence, so confirm the wording with your DM if you’re playing 2024.)
5. Whirlpool as a swimmer trap, not a nuke. The Whirlpool needs water at least 50 feet square and 25 feet deep, and it pulls anything within 25 feet inward by 10 feet a turn, then hits with 2d8 bludgeoning on a failed Strength save. It’s modest damage, so treat it as crowd control for anything in the water. Sahuagin, a swimming enemy caster, a fleeing merfolk, all of them get dragged toward the center and held there. (Rules-derived, Whirlpool effect.)
6. Rotate your effect every turn. The line people skip: you can switch which effect is running as an action on your turn, for the same one slot of concentration. Part the water this round to drop an enemy, flood it next round to sweep the survivors, spin a whirlpool after that. One cast, a rotating toolkit. (Rules-derived, opening paragraph of the spell.)
7. Make a wave that carries small boats where you want them. In a large body of water the Flood effect builds a 20-foot wave that carries Huge or smaller vehicles to the far side of your cube. That’s not always an attack. You can use it to shove your own longboat toward shore, close distance on a fleeing skiff, or beach an enemy’s rowboat somewhere inconvenient. (Rules-derived, Flood effect.)
CHEESES (clever, and where the ship-sinking lives)
8. The drop-concentration flood slam. Here’s the meanest legal trick in the whole discussion, and it comes from an actual table. Use Flood to raise the water, or empty a cube with Part Water, and then simply end concentration so all that displaced water crashes back at once. As RainbowSkyOne described running it: “I had a player do this exact thing. He emptied a 100 foot cube, then dropped concentration so it all came flooding back in.” Their DM had the ship bob violently and the crew roll Strength saves. It’s the closest thing the spell has to a burst-damage finisher. (r/DMAcademy)
9. Every ship should carry its own Control Water caster. This is the galaxy-brain take from the naval thread, and it’s not wrong. If one caster can wreck a ship, then in a world with this spell, every serious vessel wants a mage of its own to counter-maneuver. One commenter, ragnarocknroll, painted the whole picture: ships “drifting, 180s, jumps, giant wave surfing,” and when an enemy tries to ram, “have your ship do a sudden 90 degree turn all Tron style.” Control Water becomes a naval combat job class. (r/DMAcademy)
10. Whirlpool the anchor point of a small vessel. A rowboat or canoe sitting in water deep enough for the Whirlpool effect gets pulled toward the vortex along with everything else in the water. Against the little support boats a bigger ship uses for boarding parties, a whirlpool can scatter and swamp them without you ever touching the mothership. (Rules-derived, Whirlpool effect, applied to Huge-or-smaller craft.)
11. Part Water under a swimmer to drop them. If someone is in the water inside your cube and you Part Water, the water pulls apart into a trench. A swimming enemy suddenly has no water holding them up in that corridor. This is a favorite reading, and the naval thread argues it hard, but note it’s the same physics debate as the ship version, so it is a partial DM call. Great against water elementals and aquatic ambushers. (Discussion in r/DMAcademy)
12. Use range and terrain, sink the little ships you’re allowed to sink. The mechanics that actually let you wreck a boat are narrow and worth knowing cold, because they define the cheese. The Flood wave gives Huge or smaller vehicles a 25 percent capsize chance. So the spell is a legitimate ship-killer specifically against small craft: keelboats, longships, war canoes, most river vessels. Point it at the enemy’s boarding boats and dinghies, where the capsize clause bites, rather than at a Gargantuan flagship where it doesn’t. (r/DnD)
13. Roll the capsize as a d100 for the drama. Small thing, but a nice one from the mechanics thread. When you do get a capsize check, ZevVeli suggests rolling it on a d100 rather than a d4, capsizing on a 1 through 25, because “most people do the 1d100… it conveys the ‘bigness’ of what’s happening.” Same odds, more tension at the table. Others in the thread just roll a d4 and capsize on a 1, which is faster. (r/DnD)
QUESTIONABLE (ask your DM, this is the naval war)
14. Does Part Water make a ship fall out of the sky? This is THE argument, so know it cold. If you Part Water under a floating ship, does the vessel hang in the air and then plummet like a cartoon anvil? The most-upvoted read in the whole thread, from Elanadin at 549 points, says no: the Part Water option “parts the water and doesn’t destroy it. A ship in the center of the 100ft area would be moved along (displaced) with the water 50ft away.” The ship rides the water sideways rather than dropping. As quitefranklylate put it, “control water doesn’t have looney tunes logic.” Most tables land here, but it is absolutely a DM call. (r/DMAcademy)
15. Can it even touch a real warship? Read the size line before you get excited. As MechJivs argued flatly, “Control Water can’t trivialise ship combat. Huge or smaller ship has 25% chance of capsizing with Flood option… Most actual battleships are gargantuan,” which means the capsize clause never applies to them. If your DM rules the flagship is Gargantuan, the wave carries it but does not flip it, and the whole doomsday scenario shrinks to small-boat harassment. (r/DMAcademy)
16. The “hold ship” fallacy. There’s a tempting reading where you part the water and declare the ship stays put while the water leaves, dropping it into the trench. justhereformyfetish shut that down well: to rule it that way “implies control water is also hold ship. It would be akin to raising the floor but declaring the person atop it cannot move, crushing them against it.” The spell moves water. It does not pin objects in place while the water abandons them. Worth quoting at the table when someone tries the instant-kill version. (r/DMAcademy)
17. Range is the real balance lever. Easy to forget in the doomsday math: the spell reaches 300 feet. As TheSixthtactic pointed out, “300 feet is a lot shorter range for naval engagement… those ships would be on top of each other for that spell to be cast. It would be a bigger concern in port, rather than at sea.” A blue-water gun duel happens well outside 300 feet. The spell shines when ships are already close, boarding, or docked. (r/DMAcademy)
18. It’s a terrible idea if you want the ship intact. Flip side nobody thinks about. General_Brooks noted, “If the players want to capture an enemy ship, control water is a bad idea, since it’ll just sink it.” If the plunder, the prisoners, or the ship itself is the objective, Control Water is the wrong tool. It’s a demolition spell, not a boarding spell. (r/DMAcademy)
19. Treat the flood as a big wave and make the crew save. A clean middle-ground ruling from Hloden for DMs who don’t want an instant sink: run the flood as exactly what the text says, a wave, and have the crew make Dexterity saves, with riggers up in the masts risking a fall overboard. It keeps the spell dangerous without deleting the encounter. (r/DMAcademy)
DEVIANT, FUNNY, AND WORLDBUILDING BRAIN-WORMS
20. The enchanted anti-Control-Water navy. Once a table accepts this spell exists, DMs start inventing an entire counter-industry, and it’s genuinely great worldbuilding. LSunday reasoned that “ships would be designed with magically reinforced hulls to withstand sudden drops, and some kind of shielding/dome,” because it’s “hard to imagine a world with this spell where no one has devised a counter.” A whole naval arms race falls out of one 4th level spell. (r/DMAcademy)
21. Anti-magic runes and Immovable-Rod keels. The specific homebrew countermeasures get delightfully petty. Doctor_Amazo puts “anti-magic runes on the hull” and admits he caught flak for it, “rules lawyers… claiming I’m a bad DM.” WhiteGoldOne goes further: “the keel is enchanted as an oversized Immovable Rod,” so the ship physically cannot be dropped or shoved. Both are house rules, both are fun, both exist because one spell scared a DM straight. (r/DMAcademy)
22. Legislate it away. My favorite non-mechanical answer. Give_me_soup suggested pre-casting Contingency as a naval countermeasure and, better yet, in-world “laws against using a spell with such devastating consequences.” Somewhere in this setting there’s a maritime treaty banning Control Water in shipping lanes, and I want to read the trial transcript. (r/DMAcademy)
So that’s the pile, and I told you it’d be a smaller one than usual. Control Water is a precision instrument that happens to be aimed at the ocean, with maybe a dozen real plays rather than fifty cursed combos, and almost its entire online life is one enormous argument about whether it breaks naval combat. The honest answer the community lands on is that it’s strong and situational, brutal against small craft and swimmers, overrated against a Gargantuan warship, and completely dependent on your DM’s read of what “parting the water” does to whatever is floating in it. So sort that out before you set sail. What’s the worst thing you’ve ever done to a boat with this spell, and did your table let it happen? Let me know in the comments below, and until next time, roll high and stay ridiculous.
