1 Kyros: I’m not going to use fire. I’m going to use water magic to fill our waterskins for our trek across these badlands.
2 Dwalin: Wa’er magic?! Hoo’s tha’ gunna help wi’ yon scorpion?!
2 Kyros: You know living creatures are 70% water?
3 SFX: Fwa-slurp!
4 Kyros: And dead ones are 0%.
4 Dwalin: Wull tha’ spell is tootally O.P.
4 Kyros: I know! Great, isn’t it?!

There's a perennial argument that comes up in Dungeons & Dragons circles, when a player gets the incredibly cool idea that the 1st level spell Create or Destroy Water could be used to destroy water within the body of a living creature, thus instantly killing it.

Essentially, the Clever Player thinks they've justified getting the effects of a much, much more powerful spell like the 9th level Power Word Kill, with the puny expenditure of only a 1st level spell.

Now, obviously this would unbalance the game horrendously and is not the intent of the game designers. This is where the Dungeon Master will point out that the spell specifies the water must be "in an open container". Only to have Clever Player to say, "Well, creatures have a mouth - they're an open container".

Some people then fall back to saying that the spell description doesn't say you can use it to kill creatures, so you can't. And Clever Player responds by saying that the DM is stifling their creativity and penalising them for being Clever.

And so on and so forth. You can search for "destroy water D&D" and find hundreds of forum questions, discussions, blog posts, and conversations rehashing this exact same argument over and over and over again.

The game GURPS circumvents this argument by having two different destroy water spells: one that is easy to learn and which explicitly destroys water not inside living creatures, and a more difficult version that explicitly destroys water within living creatures and causes damage to them.