“He didn’t get that scar from a waterbender”
-Jet about Zuko.
But the thing is, I think he could have.
We know waterbenders can freeze water and release ice back to liquid, collect vapor from the air and create fog from liquid water. Each one of those requires changing the temperature or energy state of the water. If a waterbender can add enough energy to a system to warm ice into liquid, what’s stopping them from continuing until they’re controlling boiling water or scalding steam?