D&D 5E Control water and sea battles

[FreeTheSlaves]

Okay, this 4th level wizard/cleric spell seems super-powerful in sea battle at first glance. The 'Flood' option in particular can wash vessels up to 300' in a direction of your choosing with a 25% capsize chance.

But I personally don't want it to be an 'I win' move which inevitably results in 2 opposing spell casters fling each other's ships about willy-nilly. So, I got to thinking.

Size matters. Specifically greater than huge size, you're not getting moved by this spell. Now the MM defines monster gargantuan size as 20' x 20' or larger.

Quick internet search tells me longships were classified by oars and crew capacity;
- Busse 160' long with 35 pairs of oars holding 80 vikings,
- Skeid 100' long 30 pairs of oars 70 vikings,
- Snekkja 60' 20 pairs 40 vikings (very common build)
- Karvi 60' but more narrow than the Snekkja 12-32 pairs

Off hand, I'd say the Busse and Skeid are gargantuan simply on grounds of holding 70-80 guys. The common Snekkja seems to be what the PHB longship is modeling and it's anybodies guess whether it's bigger than huge.

As for the 25% capsize chance, I'm inclined to think that a summoned water elemental (the CR6 mage could cast) would negate that if it were instructed to use its action to stabilize a ship's hull. Of course this would require forewarning as elementals are summoned for only an hour.

Has anyone run sea battles with Control water? How did you rule on size? And what tactics or counter-measures emerged?

 

[Tonguez]

UA defines a 60x20 Keelboat as Gargantuan and a 10x5 Rowboat as Large
A Galley 130x20 is also Gargantuan

it looks like most ships are too big to be affected by Flood

 

[FreeTheSlaves]

I admit I'm no physics major so my rationale might be mis-calibrated, however...

Gargantuan sized monsters are at least 20' x 20' on the grid, and we should consider this cubed to reflect their mass. So that's 16 medium-sized people x 4 = 72. Now that's fighting space so you could double it again (even quadruple?) to get a compact gargantuan mass.

Coming back to the 60 x 20 keelboat, it exceeds the length and meets the width - but what about height and mass? Seems on the flimsy side for gargantuan. It's comparable size-wise to the Snekkja. If it had a full complement of 40 crew and full cargo there would be less doubt.

I'm a-okay with a galley being gargantuan, it compares well to the Busse and Skeld, which right off the bat have 70+ crew and very lengthy keels. They are big ocean going vessels. Add cargo and it's a slam-dunk.

Buuuut, I'm guessing UA has defined the keelboat along playlest lines, what best for the game, rather than size categories.

So maybe Control water is a 'whoopsie' and WotC have clawed back some of its power?

 

[MarkB]

One thing to consider is that ships are specifically designed to float in water, whereas monsters are not. They're going to be easier to push around.

 

[FreeTheSlaves]

True, but Control water's Flood option specifically calls out vessels:

Flood. ... Any Huge or smaller vehicles struck by the wave have a 25 percent chance of capsizing.

 

[FreeTheSlaves]

I guess at this point, my bone of contention is vessel size. If only a row boat is considered huge or smaller, well however you rationalize it, that's a big nerf.

 

[Tonguez]

It does seem a bit of a major nerf, which is a bit of a bummer for Druids in a nautical campaign who might want to use it against enemy shipping.

I suppose the spell still gives area control as ships float down the surge, but personally I’d be happy if Keelboats were considered Huge rather than Gargantuan.

Apparently even Rafts and whaleboats are considered Huge whereas Dugout canoes are only large. Despite all of them having single digit crew size.

 

[FreeTheSlaves]

They're just looking at the vessel draft and saying 'it fits the huge dimension on the grid' and ruling based on that. Mind you UA is not RAW. In fact RAW is silent in this matter.

Yeah, I don't buy it.

I guess I'm settled on ruling the Galley and Warship are gargantuan. Sailing ship and Longship are huge, although a full crew complement and/or cargo will push them into gargantuan. And Keel boat and Row boat are bottom end of huge and large respectively.

Thanks for the replies all. It's helped me reach a consistent ruling with sizes at least.

We haven't covered Control water tactics, and I also think summoned Water elementals must enter the equation.

Regarding gargantuan vessels, the 'Part water' option can effectively immobilize them. This same option can also allow a ship to hide, if it can lower its mast. Now that's a funny image.

 

[Evilhalfling]

I realize I'm Necroing, but this is still a hard topic to adjudicate.

Next session is two ships: the PCs 20x60 (with 2 decks) and a larger pirate ship 30x90 (3 decks)
both sides have access to control water. (not sure if PC druid will memorize it though.)

Neither side should want to destroy the other (at first) because the PCs would like a bigger ship, and the pirates don't want to sink the treasure.
I'm going to HR that control water can just be used to end a similar effect as if it was dispel magic. but if the battle goes poorly for the pirates, and their Kraken priest is still alive he is going to use this spell to do as much damage as possible.

I might agree to call a single-decked Keel ship (20x60) huge, but these two clearly larger.
so Flood is useless, Whirpool is a 50x50 cube that pulls things within 25' toward it 10' per round. Creatures get a str check to break free. (vs spell dc)
I think a ship should use a sailors skill check to break free instead. This would be a great spell to pull both ships closer together and lock them in a boarding action. (while spinning) if they both start within 100' of each other. This spell will close the gap quickly (not instantly). the damage of 2d8 will be ignored by the 15 hp threshold of ships

the problem is with part water. Either ship could fall to the bottom of a 100' deep trench (it could be less due to the presence of islands).
Either ship can technically absorb the falling damage, but the entire crew is going to splatter. (other than PCs & maybe captain)
and the chances of it being capsized/submerged when the spell ends.. at least 25% perhaps 75% the caster could make it worse by only putting 75% of the ship's length in the trench so that it enters with a near vertical dive.
If I want to make the spell as benign as possible (ie useful, but not an "I win" button) then I could say that the water parts gently, and settle the boat on the ocean floor (or lower-level waters surface, then lifts it up again when it ends. Functioning like a Hold Monster spell, no save for ships.
But still trying to sail out of the trench could only be a catastrophe - unavoidable if the ship is already moving. (except by DM fiat)
a ship entering a wall of water, and floating (not necessarily right side up) 100' to the surface, is pretty much toast, unless designed for underwater travel.

Suggestions or thoughts?

 

[Stormonu]

Nice necro!

I'm always in favor of a saving throw for the victim to attempt to mitigate the effect in some way.

Part Water does mention the trench fills back in slowly over a round, so it could be ruled it parts slowly as well. Vessels not completely in the area of effect might get a save (Water Vessel skill check?) to maneuver to safety (remember, things on a grid are static, in "real" life they're in constant motion). If the vessel is over 50% over the area, the save might be at disadvantage. If you want it to do damage, I'd have (seperate) saves (Dex) for the crew to ride out the fall, and maybe up to 8d4 falling damage on a fail. Success on the crew save indicates they've somehow managed to ride the descent safely. It'll still wreck an no-name NPC vessel pretty badly, but more skilled crews would be able to avoid disaster, as it should be.