Waterproofing

I am doing an RV conversion my bathroom shower wall is wood stained green I need to know what I can make this waterproof with that will be shiny and clear and not mess up my green stain.

How to finish a teak bathtub

Hello, I know nothing about woodworking or finishes. I am purchasing a bathtub made of Iroko wood and I am worried that 1. I won't be able to use soap and shampoo without damaging the wood, and 2. that the wood will erode over time. I know that wooden bathtub companies like this one (americanwoodtubs.com) use a fiberglass finish on their tubs. Can I just paint some kind of similar finish on the Iroko tub (which is already finished with linseed oil and lavender oil). If so, what finish should I buy/use? Or, will the tub be OK as-is? Thank you so much for your help! - Sarah