Though I don't know alot about water dragons, I do know they are not really a beginners lizard. The male water dragon can reach lengths of up to three feet with females about two feet in length. The length is mostly tail. Being a more tropical species, water dragons do need much higher humidity and access to water, enough to swim in. Not sure how well they take to handling but I suspect it isn't as tolerant of handling as bearded dragons.
As water dragons do get bigger than bearded dragons, they will need a much larger cage. From what I can learn of water dragon cage sizes, they need one that is at least 6'x3'x4' in dimensions.
Bearded dragons on the other hand, only need an adult cage that is a minimum of 4'x2'x2', grow to around 18-24" in length and are much calmer and easy to handle. As they are from semi-arid conditions, humidity must be low, preferibly below 50%. They do need a higher basking temp and ambient temperature (basking: 95-115F, ambient in mid to high 80'sF and cool side of mid 70's). This is easily accomplished with basking lights (regular household bulbs do fine, wattage depends on house room temperature and cage size. I used a 125W flood light type bulb in a cage measuring 5'x2'x2' and easily maintained a basking temp of around 110F at the highest point of her basking log, with 95F towards teh lower end of the log. It was a large wide piece of driftwood I used, which is great, as it allowed my bearded dragon to move about on the log to reach the temps she wanted to bask in).
Bearded dragons adults eat much more vegetiable matter than water dragons. Once adult, bearded dragons will need about 90% of their diet consistanting of calcium and nutrient rich greens, vegetables and fruits, with the last 10% being insect prey. Water dragons need much more insects when adult as well as whole prey, with only about 10% of their diet vegetation and fruit.
Bearded dragons are not as likely to run when picked up, and with regular careful handling can become very docile and spend many hours sitting on a lap or shoulder (be careful when moving around with a dragon on your shoulder, I suggest using a harness, just in case something startles your dragon and he jumps, especially if outside). Bearded dragons are not as prone to bite, though they will flare out their beards, hiss and sometimes mock lunge if they feel threatened or nervous. Even if they do bite, they do not have strong jaws and even adults will rarely break the skin.
I suggest reading the book on Water dragons you bought and research care sheets for both water dragons and bearded dragons and decide which one suits your experience and ability to keep. If you still really like water dragons but dont' feel ready yet to get one, you can still get one later on, after you had some experience with bearded dragons and want to add a new reptile to your home.
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PHLdyPayne