You don’t need all 5 elements, however, that is optimal, and you wouldn’t get as much without it, but the Abyss is mana rich…
So therefore, there must be water, or liquid, somewhere in the Abyss. We do know there is mercury, alkalai, acids and other things like this.
Interestingly enough, molten lava has elements of Water and Earth, as does mud. (not from a physics point of view, but from a metaphysical point of view: fluidity.