Subverted: Misty's powers are not water, but they are connected to water (e.g. ice, snow).
Double Subverted: But she eventually trains herself to be able to control water.
Parodied: Misty can manipulate fire to behave as water.
Zig Zagged: Misty is supposedly able to control water, but she is an Ice Person, though she can use her ice powers to do what water supposed to do like extinguishing fire.
Averted: Misty has no water powers.
Enforced: "Let's have one of the superheroes use water as a weapon."
"Well, of course we have a water mage! It's one of the four elements! Someone is bound to have it as their power!"
"Look on the bright side... At least when I'm done with you, nobody will know that you wet yourself."
"Those of you in the splash zone will wish you'd stayed home today."
Misty gains water powers by touching a mystic water crystal.
Misty has no magic whatsoever... But she does have access to a fire hose. Good enough.
Exploited: Misty's rival learns to Shock and Awe to have an advantage.
Defied: Misty has water powers, but refuses to use them.
Discussed: She sure can use water, can't she?
Water doesn't have the immediately-obvious destructive nature of fire, so even though Misty is capable of being a world-destroying Black Magician Girl, she gets lumped into being The Medic for entire arbitrary reasons.
Misty is actually a master swordswoman who wields water as her element. For similar reasons, nobody puts her on the frontlines where her skills would be most useful...
Misty can create giant tidal waves, firehose-like sprays with insane water pressure, floods, and storms, and that's when she's not even trying to think outside the box. It's not entirely clear if she realizes she could cause a drought, but other people have, and they're not exactly thrilled at the prospect. Not to mention that the human body is made up of mostly water. Because of this, she's treated as a Person of Mass Destruction.
She decides to take advantage of water's sheer versatility; becoming The Red Mage.
Despite the sheer destructive/cruelty potential inherent to her abilities, Misty also has a strict honor code that prevents her from her crossing that line, which in turn manages to gain the trust and respect of people, as they know she'll only use that kind of power when it is absolutely necessary.