# D&D 5E5E underwater thoughts

#### James Gasik

##### We don't talk about Pun-Pun
Supporter
Cone of Cold also leaves behind an icy surface of difficult terrain.

#### Ancalagon

##### Dusty Dragon
No, I never said it did, but it would flash boil anything nearby.

Sent from my iPad using EN World

The amount of heat needed to flashboil a 40 feet diametre ball of water is *immense*.

#### Ancalagon

##### Dusty Dragon
It takes 4.184 joules to increase the temperagure of 1 gram water by 1 celcius

Say we are in 15 C water. It would take 355.64 joules to increase the water temperature of 1 gram of water to 100 c

But we want the water to *boil*. The heat of vaporisation of water is 2257 joules per gram!

So this gives us a total of 2613 joules per gram of water.

But we have a 40 foot sphere. that is 948 425 582 grams of water, or aprox 950 tons.

This leads us to the astounding figure of 2 478 236 045 386 joules. or, if you perfer, 2.478 TERA joules, which is roughly half a kiloton of TNT

I think we can all agree that fireballs aren't small tactical nukes?

S

#### Sunseeker

##### Guest
The 6th-level spell Freezing Sphere is cold damage that explicitly freezes water into ice.

Inferrably, all lower level spells only great slush − not solid ice − thus difficult terrain that obscures vision.

That's a good point. And I think slushy difficult terrain (that dissipates of course since ice floats) will help keep Freezing Sphere unique. Putting someone in an ice-sphere should I think be a tactical decision and not just a whim of the dice. As far as Cone of Cold goes, leaving an "icy surface" would I think be on-par with creating a conical area of difficult terrain. Swimming through slushy water as difficult terrain is I feel, equitable to attempting to walk on icy ground.

EDIT: Thankfully WOTC beat me to the punch with Freezing Sphere. It's a freaking 60ft radius (that's a 120ft diameter sphere!) and the ice is on the "edge" in 6" thick, so it'd just be an icy bubble. No worries about 1-shotting whole squads!

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#### tglassy

No, but it would effectively trap whole squads behind a 6" thick wall of ice!

Sent from my iPad using EN World

S

#### Sunseeker

##### Guest
No, but it would effectively trap whole squads behind a 6" thick wall of ice!

Sent from my iPad using EN World

Yeah but it has a Strength DC equal to the spell DC to break which seems reasonable.

#### lonelynoose

##### First Post
Has Physics quiz tomorrow. Will pass.

#### OldFool

##### First Post
Thank you, Ancalagon. I have been sitting here reading the comments of other very verbal people with zero actual knowledge of physics. The water would absorb the entire effect of the Fireball and perhaps heat up a few degrees. But, seeing as water is denser than wood, as soon as the streak leaves the caster's finger and hits the water, it is just like hitting a wooden door. It goes no further, so warms the water in the area of the caster a few degrees.

Furthermore, humans are less dense than water. If a Fireball would flash boil the water, it would also flash boil all living creatures in the area. Death no save, baby.

It takes 4.184 joules to increase the temperagure of 1 gram water by 1 celcius

Say we are in 15 C water. It would take 355.64 joules to increase the water temperature of 1 gram of water to 100 c

But we want the water to *boil*. The heat of vaporisation of water is 2257 joules per gram!

So this gives us a total of 2613 joules per gram of water.

But we have a 40 foot sphere. that is 948 425 582 grams of water, or aprox 950 tons.

This leads us to the astounding figure of 2 478 236 045 386 joules. or, if you perfer, 2.478 TERA joules, which is roughly half a kiloton of TNT

I think we can all agree that fireballs aren't small tactical nukes?

#### Ancalagon

##### Dusty Dragon
Thank you, Ancalagon. I have been sitting here reading the comments of other very verbal people with zero actual knowledge of physics. The water would absorb the entire effect of the Fireball and perhaps heat up a few degrees. But, seeing as water is denser than wood, as soon as the streak leaves the caster's finger and hits the water, it is just like hitting a wooden door. It goes no further, so warms the water in the area of the caster a few degrees.

Furthermore, humans are less dense than water. If a Fireball would flash boil the water, it would also flash boil all living creatures in the area. Death no save, baby.

The problem is what is obvious to some is not to others. So that "do not cross this is " line is not in the same place for different people. So to be a fireball boiling off water is completely ludicrous. But for others... it's cool.

#### 77IM

##### Explorer!!!
Supporter
If a Fireball would flash boil the water, it would also flash boil all living creatures in the area. Death no save, baby.

Note that the average damage from a fireball is enough to insta-kill human commoners, most medium-sized animals, and some 1st-level PCs, even if they make their saving throw. For larger animals, the damage on a successful save is often enough to drop them to 0 hit points, even if it doesn't kill them outright. So, that's pretty close to "death no save."

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