This is somewhat on topic... Not sure what the fourth and fifth actually are, but in the Shivering Isles we discover the "sixth element." Flesh.
A quote from Haskill about it" "She is a powerful sorceress. She believes she has found a "sixth element," the element of Flesh. She was expelled from the Mages Guild for this belief, and for the... extreme nature of her experiments" [...]" - http://www.uesp.net/wiki/Shivering:Relmyna_Verenim
Fire, Water, Earth, Air, Light, and then Relmyna's Flesh. And the Ayleids also suspected that fire was just a corrupted version of Light.
Water is not a new element. Water is all over the place. It's part of the Frost spells. Shooting water at your opponents isn't going to do much when you could freeze them to death instead.
And why are the Dwemer your solution to EVERYTHING? It's suspected that the Dwemer didn't even use magicka, why would they have a scroll for some lost element (which, as already stated, is not lost.)