Ice spells/Supernatural attacks underwater, what happens?

[RUMBLETiGER]

I'm running an encounter with a White dragon in it's lair against my players. I've enjoyed designing the Dragon's lair, and one part is a water filled tunnel under the ice in the main chamber. Once the Dragon appears to be losing the fight, she'll retreat into the waterway and either escape out her back door to fight outside, or try to lure the PCs into the waterway.

So here's my question: are there RAW someplace that talks about freezing water with magical/supernatural effects? I'd imagine if a Cone of Ice breath was exhaled underwater, it would result in the creation of a lasting ice chunk in the cone's shape (and the dragon quickly needing to go up for air, she did just exhale, after all). However, I don't want to toy around with this, I'd like to find some existing guidelines if such already exist.

I have a second question about designing this encounter Here.

Thanks in advance.

 

[Nagol]

Freezing Sphere (a 6th level spell) talks about freezing open water. The cone is likely to do substantially less but a case can be made for creating a lot of small frozen beads that would pop to the surface and create concealment / difficult terrain.

 

[RUMBLETiGER]

That's a useful starting point. Are there any other clues in spells or effects with similar descriptions?

As a level 6 spell, dealing 1d6 damage per level, this is a minimum 11d6 by the time it can be cast. My adult White Dragon is dealing 6d6. If I wanted to extrapolate something from this comparison, it's so far not very promising that the breath weapon would do what I am imagining.

Which would be just fine, the encounter will be exciting enough without creating underwater ice chunks.

 

[Umbran]

I summon... [MENTION=2072]Aeolius[/MENTION] ! If there's an expert on such around here, it'd be him, I think.

 

[Aeolius]

You might find some answers in an older thread on the same topic .

 

[RUMBLETiGER]

You might find some answers in an older thread on the same topic .

Thanks, I had tried to search for those who have discussed before, found a sort of on topic thread in GitP, but not the answers I wanted.

I'm becoming convinced that there is no RAW for this, so I'll err on the side of one cannot freeze water with magic unless the spell says so.

Thanks all!

 

[radja]

although strictly speaking it doesn't freeze water, wall of ice would work just fine to trap characters below an ice surface. Also... wall of ice would be a self-repairing ice-sheet for the duration.

"Even when the ice has been broken through, a sheet of frigid air remains. Any creature stepping through it (including the one who broke through the wall) takes 1d6 points of cold damage +1 point per caster level (no save)."

 

[Grogg of the North]

The way I would handle this is to ask for a spellcraft check. If you make it, the spell creates a block of ice in the area that is damaged by spell. I'd set the DC equal to the DC for casting fire spells underwater (20+level).

 

[Greenfield]

One difference between the dragon's breath weapon and a spell like,say, Cone of Cold, is that the Dragon's breath is, well, breath. That is, it's a blast of super-cold air. The spell, on the other hand, is just cone-shaped cold energy.

So the Dragon's breath is going to foam/bubble the water as it freezes. You'll get something of a "Slushie" effect, rather than a solid block of ice. A spell like Cone of Cold on the other hand might freeze the water solid.

I'd consider the water temperature prior to the effect: If it's glacier-melt water high in the mountains, you're creating a new glacier. If it's condensed steam from an active volcano or geyser water, you probably won't see much ice (if any).

 

[Empirate]

OP, why not just leave rules as written be in this case and just say that's the way it works? It's a cool encounter idea, after all, and one that feels 'right' and natural to boot. I doubt your players will go "hey, that's not in the Monster Manual! White Dragons can't freeze water with their breaths like that!" and rules lawyer it out. If they're at all good players, they'll probably roll with it and just remember a very cool encounter which had actual physics in it.

If all else fails, just give the dragon a homebrew feat or something:


Freezing Cold (Monster)

Prerequisite: Cold subtype, (Su) special attack that deals cold damage in an area, Con 19+

Benefit: you can use your supernatural cold attack to freeze large amounts of water quickly. Instead of its usual area, the attack affects one contiguous 5'-cube per 2 HD. The attack deals only half normal damage in this area, but all water within the area is instantly frozen solid. Creatures that fit completely within the area can avoid being encased in ice with a successful Reflex save against the attack's normal save DC. Creatures that fail this save must hold their breath (apply suffocation rules) if they need to breathe. Success results in that creature's being pushed aside (in a direction of the creature's choice) to the outer limit of the effect. Creatures that only have part of their space within the affected area are entangled and immobilized (Reflex negates), but can break free with a successful Escape Artist or Strength check (DC 20). The ice has as many HP as the attack dealt damage.