Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about how to build an outdoor shower.
This is the perfect time to build this project. Building the plumbing for it is actually not too difficult. Finding a location and building the shower itself is open to discussion. One of the best D.I.Y. outdoor showers I've seen is this one - outdoor shower by @peta. They used solid galvanized fittings on a very sturdy wall. My favorite part is that they used a very large paver surrounded by large river stones as the floor area. I'm quite sure they have taken drainage into consideration when they built this.
Would it be possible for you to post a photo of the proposed location of the shower? Were you thinking of an open shower or semi-private enclosure? Have you considered where the water will go as you shower? These are just some of the things to consider when building your outdoor shower.
Please keep us updated with your plans, we look forward to seeing the photos.
I suggest having a look at these previous discussions about outdoor showers: