Welcome to the Bunnings Workshop community @freddie. It's great to have you join us and many thanks for your question.
It would be helpful to hear a few more details on the what type of waterproofing you would like to do on your laundry walls. Typically in bathrooms, you would waterproof floors, shower enclosures, around your bath and the toilet area.
If your laundry walls are plasterboard then they can be painted with a suitable bathroom paint which includes a mould preventative.