Ais said:
I always see Judgement as water, even instinctively. Its ruling planet is Pluto, and Pluto relating to fire is counter-intuitive to me (since it's an ice planet and is the furthest away from the sun).
However you see the card, and personally want it to be is fine with me. However, I'm still going to say that the water association, for me, personally, doesn't make sense even given your explaination, and I hope you won't mind if I say why.
Pluto, by way of its name, relates to the god of the underworld. So even if you go for the Pluto association, I don't see how you get water. It is named for the god of the underworld, meaning Earth.
If we're going for actual planets, rather than mythology or astrological associations, then it's still confusing. Uranus is considered an "ice giant" yet The Fool, which it rules, is considered to be Air. Meanwhile Pluto is less an ice planet than Uranus. It's a mix of rock and water. Why pick the water part of the planet rather than the rock part?
Finally, I don't see how Judgement is water when it's name suggests people rising up out of the Earth at last judgement. Understand, I'm fully behind questioning Judgement as "Fire," though, as LRichard pointed out, that was it's original element when it, the Fool and The Hanged Men were appointed elements rather than planets. But if one is going to argue against Judgement being fire, why argue for it being water when water is not associated either with Pluto, the god of the underworld (apt for the dead rising from graves) or the dead rising from graves. Wouldn't it be more apt to argue that it ought to be Earth?