Bathroom shower shelf

This is the project that came into my mind literally under the shower. :) I wanted somethig that would keep my shower accessories and shampoo just in the reach of hand in my small shower cabin. The small bathroom / shower cabin shelf is just enough to store 400ml shampoo and some other shower cosmetics, or literally just some soap and sponge. The back wall of the shelf is created in a way to be able to mount on the wall using some strong, at least 1mm thick waterproof double sided tape without the need of drilling any holes. Possibly can be mounted with some screws as well.