Keep in mind that this isn't a magic based site so water is still, very much physical and just being manipulated.
Whereas on a magic based one a magical water attack and a nonmagical water attack are different (weird I know but that's how it works)
Even more so depending on the type of attack these boots might even protect your more so from water, air and fire than they would say an Earth or a really strong punch or kick.
In short, this type of protect doesn't make sense and would like a revision to make it more site appropriate.