Yeah there are a few methods for making realistic water.
There's the old standard which is PVA and paint
Or there is always the woodland scenics water stuff
Also a good substitute is fishing bait liquid jelly, it can be dyed beforehand, and comes by the gallon, pretty cheap too, sure it'll form a jelly, but hey that would make for some freaky terrain, since you can mold it, perhaps small jelly like surfaces for fighting in deep warp space where solids could form.
Also something for dying PVA you can actually use some of the leftovers from that blue tissue paper, let it sit overnight in the PVA (if you can, use elmers glue, the real elmers glue this one works for sure) and you'll have blue glue, you just have to shake it up a bit before hand, probably use a 1/2 filled glue tube, maybe base it with 1/2 white PVA, then put the rest on top. I remember making my teachers so mad in school when all their glue would be green, pink, blue, orange, black, etc. Very funny, and I was never caught.