We don’t have much standardised information about what showering facilities are used, as each site is different. Assume that there are not any showers at any of the remote sites. Some of the larger ranger bases have existing shower facilities, but this design area relates to sites that are either being constructed, or a rarely used, so installing permanent showers isn’t a good use of resources. It would also be safe to assume a combination of river/creek bathing (where crocodile risk is low) or road bathing (wet wipes/damp cloth) is the current methods of bathing.
Your solution should be exploring a simple to use and set up solution that could potentially attach directly to a water tank or plumbed system, and dispose of waste water in a environmentally appropriate manner.
In terms of tank size, use the photos in the design area to ascertain what your design should be compatible with. It will likely rely on gravity for flow, and the sizes of tanks could be as little as 1000 litres and up to 10,000 depending the site and the existing infrastructure. Your solution should work with the minimum setups, which could be a ground level, 1000 litre tank. Can the solution operate without a gravity fed water system?
Reach out if you’ve got further questions.