I imagine that if you got the water by melting down a core sample from an old enough glacier, you could get pretty holiness-neutral water.
Over on Dave Wilton’s WordOrigins message board, that would be called a mantle, as in “a mantle of invisibility”. I’ll wear it proudly as well as inconspicuously.
What about all the Spanish and Portuguese galleons, and the French, etc., that sank while carrying priests? Who had holy water in their priest kits? Unless Davey Jones kept all that holy water locked away in the proverbial locker, it must have mingled with the ocean water many times over. That must be where Kurt Vonnegut got the concept for ice nine from.
As Frank Zappa jammed, “The Ocean Is the Ultimate Solution.”