I do not personally keep water water dragons however from reading the forum the minimum recomended viv size 5 ft long, 3 ft deep and 4ft high this makes sure that the lizard has enough space to turn around full and move. Your viv is a bit small as the lizard can not lay out fully extended this can cause problems as it will not be able to thermoregulate correctly. Nor can a thermal gradient be created. If you have a look through the "Habitat"section there are many impressive examples of suitable housing.
yeah man upgrade pronto, these guys are arboreal and need a lot of space. Lizards generally grow very quickly and exercise is really important to them as well as being able to control their body temperature.
it should be high and when done properly aboreal lizards should behave like this:
it should move up to warm up and down to cool down, much like it would do in the rainforest canopy.
i have one cwd at 2 foot long and my cage is 6 foot high 4 foot wide 3 foot deep and is plenty of room. Seriously need a big cage i found my cwd was alot happier when moved into a nice big viv. You do need to upgrade asap mate. Otherwise your gonna have one angry lil wd.