Yes...marble in a wet room needs sealing. There are many marble experts (stone experts are different from tile experts) who will tell you the marble needed to be sealed several times BEFORE it was installed, and then several times AFTER it is installed. And then sealants are used at regular intervals for a few years until the marble has been saturated with sealant and doesn't "need" it any more.

Obviously the "before" install is no longer an option. No worries. You simply have to find the RIGHT stone sealer and apply it as many times as required. Then allow it to cure (could be a while before you use the shower) - and off you go. Keep reapplying as scheduled (by the sealant manufacturer) and enjoy your very pretty stone.

Because this has been sourced/suggested by others (who deal with tile and not stone), I recommend you find some stone/granite professionals and start asking questions about your stone. After speaking with multiple professionals in your area, you should get a handle on what is needed and what is FORBIDDEN. Yes...there are plenty of things that are forbidden with marble. That knowledge is SUPER important.

Hopefully Joseph or the Tile experts will pop in and offer some strong recommendations for sealant.

Thank you so much! There is a stone place not far from where I work, I'll pop in there next week. We actually aren't moving into this bedroom for a while so it won't hurt us to wait to get it sealed properly.

This is a lovely shower.