I am gming a group and they are faced with a Medium Fire Elemental. One of the casters (level 1) wants to use create water on the ground to stop it in its tracks...
A fire elemental cannot enter water or any other nonflammable liquid. A body of water is an impassible barrier unless the fire elemental can step or jump over it or the water is covered with a flammable material (such as a layer of oil).
I said because a grid square is 5x5 or 25 square feet, 2 gallons of water, which is all he can create at level 1, wouldn't be enough water from a single source on a single turn on a single grid square to stop or even slow down the elemental.
If the ground is flat, the puddle will be wide, but extremely shallow, and the elemental will likely evaporate any water before it touches him
If not, the water will accumulate in smaller, slightly deeper puddles, which the elemental can easily step around.
Either way, I can't see an 8-foot pyre being inconvenienced significantly by a couple of gallons of unpressurised water