How to finish the shower

I feel like I'm missing the bus.  I've read a bunch and looked at youtube (mylittlehomestead is so fun) but I still can't figure out how one goes from bare mud to finished shower.  I want my shower to be up against the exterior wall, maybe with a nice window.  So let's say I have the hyperadome round wall, and I put a drain in the dirt below where the floor will be, as high as where the top of the floor will be. What then?

In my head I'm thinking, some form of concrete plaster on the walls and floor, then maybe cover everything with a broken tile mosaic.   But I keep imagining seepage from the shower eating into the hyperadobe and causing the entire structure to collapse. Unless I can catch that bus and get clued in. :)  So what do others use to finish the bathroom whilst ensuring that the water and the earthbags never mix?

Prob no different than with a studded wall. Shower pan can be poured concrete but this absorbs water, so a rubber liner is placed down before pouring. Mosaic can be applied over that.

Having a waterproof barrier is important.
I have found anything other than either solid membrane will leak.
Painted on waterproofing seems to suffer from movement cracks or poor installation.
I have used the following;
- Steel sheet
Cement sheeting
corrugated iron sheets
- old glass shower screens painted on the back and fixed to the wall.
Corners and bottom lips are weak points that need special care

If you want a for sure thing, google schluter shower systems. They are lightweight, totally waterproof, but are pricey.

If nothing else it will give you a good understanding....