There are many "super soil" recipes that can be water only. Subcool's mix works well and gets a lot of attention, but that doesn't mean it's the only option.
You could simply take some Ocean Forrest soil and mix in some Espoma Plant Tone dry fertilizer to create a "super soil".
Or buy the pre-bagged Subcool soil that seems to be on the market now.
I use my own version of a "super soil", and mostly just add water. This site is loaded with info about mixing soils. Time for some reading!