We should add a check for this, the huge piles of water are just to abusable and far too taxing on servers.

Not to mention in the Nether.

isn't casting water jet in midair kind of the whole point? It's supposed to be a jet... I was imagining source blocks be placed in a parabola from where the player is looking and they would shortly thereafter disappear. (they just wouldn't spawn next to existing water)

If Hypersonic wants to try a rewrite of Waterjet to use a parabola, I'm all for it. He's better with the math-y aspects of such spells.