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human
[Avatar: The Last Airbender/The Legend of Korra] Why can't Waterbender's boil water?

We see most semi-proficient waterbenders able to change the state of water from liquid to solid and then vice-versa. However, what's stopping them from having the ability of boiling the water whilst its under their control and turning it into a gas?
gpt
We see Katara do this in season 3, to screen their escape from a Fire Nation ship. Waterbenders can also control clouds and mist.

You don't see it very often because it has few hand-to-hand combat applications. Waterbenders also can't make water vapor hot enough to harm someone (because that needs fire), and it's more direct to slap someone with a water tentacle or freeze them.