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Zer0tonin I second what Mark has said. Just recently I replied to a question about crossing these two types:
https://aussiepythons.com/forum/threads/ewdxgwd.227506/post-2539484.
Given that males can attain a total length of 1m and females almost 2/3 of that, and that they are reasonably active, these animals are not suited to small enclosures as adults. In order to keep more than one, you would need quite a sizeable indoor cage or pit, or a good-sized outdoor pit. With regard to keeping them outdoors, I have seen GWDs from the far south of NSW do very well outside in Sydney. If intending to house them in a backyard pit, your choice of subspecies should be based primarily on the suitability of your local climate, and then on your personal preference.
You do not have to provide a huge water area, just sufficient for the animals to be able to totally immerse themselves. If you can provide more water, maybe even a swimming area, that would be great but is not essential. They do have a habit of defecating in water and this will need to be addressed.
In nature, dominant males establish a section of a water-way as their territory. They will chase off any other males that enter this. If the intruder challenges the reigning male, then a fight is likely to ensue, and this is where bits of the body can go missing. A dominant male will allow several females to take up residence within its territory. However, the females will establish their own pecking order of dominance and are restricted to smaller areas within the male’s territory. Visual blocks within an enclosure are very important for reducing the negative effects of dominance interactions. Grasses, reeds and shrubs at appropriate intervals, that block the vision of lizards sitting on rocks or overhanding branches along the waterway, will allow different individuals to get along a lot better.
Just like Bearded Dragons, Water Dragons have developed a complex system of sign language. They communicate by head bobbing, arm waving, push ups and tail flicking. The rate at which they perform these movements, and the context in which they are performed, are part of defining their meaning. This sort of social communication is not at all uncommon amongst agamid lizards.
There also seems to be a measure of overlap between different species. While I cannot recall which specific forum it was, a member involved had an EWD and a EBD in cages that were placed on opposite sides of his reptile room, such that each lizard was fully visible to the other. After he had rearranged his cages this way, he noticed a downturn in the well-being of the EWD. It showed signs of stress, not eating and becoming listless, instead of its usual perky self. It then began to lose body condition and he became concerned it might die. Given that it had previously been doing fine, I enquired as to what had changed in its environment. After a bit more questioning it was revealed that the EBD was performing behaviours that the keeper had not previously seen. It was therefore suggested that he change things so that these two lizards could no longer see each other, so he did so. It took a couple of weeks but the EWD began to improve and start eating again, and ended up getting back to normal. Clearly a salutary lesson in the potential effects of dominance behaviour. This example underscores the wisdom of Mark having placed his EWDs so they cannot see each other.