The spell starts the fire; it need not sustain it
A magical flame can have an extraordinary cause and still obey an ordinary weakness. If a spell creates fire but does not also shield it from water, the flame can be treated like any other: it needs conditions that let it keep burning. A shallow pond can therefore put it out without making the magic itself seem weak. The spell did its job; it simply did not make the result invulnerable.
That distinction gives players a rule they can grasp. Magic changes where the danger comes from, not necessarily what can stop it. Water remains useful even when the threat is supernatural, so players can read the scene and respond rather than guess at an entirely new set of rules.
A small pond becomes a gameplay tool
For designers, this kind of interaction turns scenery into a practical choice. A pond is no longer just something to walk around: it can offer a way to escape, interrupt an attack, or test how a threat behaves. Because the water is shallow, the payoff is especially legible—the character need not dive into a lake or find a special artifact to use the environment.
The limit matters, too. If every magical effect ignored familiar countermeasures, players would have to memorize exceptions. Letting even a demon’s conjured fire go out in a pond makes the world easier to reason about—and gives an ordinary patch of water a surprisingly heroic job.
