Chinese water dragon sleeping submerged

Question
Hi,
My chinese water dragon was not on its normal sleeping perch tonight.  I found it submerged in it's pool, apparently alive.  It opened its eye when I disturbed it slightly [the eye was not as bright as usual but I did wake it up]; after a brief period rose to the surface and stuck it's nose out).  Is this normal behavior for a chinese water dragon?

Details about my pet - I have had it for about 5 months, it has shed once already and has a good appetite.  It seemed just fine this morning eating two crickets and a superworm and chasing additional crickets (which it probably caught after I left for work).  
It is housed in a 55 gallon tank which is heated by a heater in its pool (78 F) and a closed gallon jar with a submerged fish tank heater set at 80.  The tank thermometers read 80 (they are at opposite ends of the tank), the basking light has been off for two hours at this point.  The humidity is a bit low (around 50% most of the time).
The temperatures had been running around 85 at night but I have been trying to lower it after I read that they preferred slightly lower temps.

Answer
Hello Ellen, he probably has been spending so much time in the water because of the low humidity try bringing that up a bit. (lowering the heat will also help humidity rise)
Water Dragons can hold their breath underwater for up to half an hour. But you still want to keep an eye on him when he is submerged. You have branches or rocks for him to get out easily correct? Could you put in a floating fake lilly pad or something for him to be in the water but not have to worry about swimming? Your setup from your information sounds good but how old is he? At a young age (anywhere under 18 inches Snout to Tail) he should be shedding once a month to once every two months. If he is large then it wont be as often however. I have never heard of a water dragon sleeping underwater but many do love to stay under for extended periods of time and come up for air periodically. Just make sure there is an easy way for him to get out of the water if he wants too and keep an eye on him. It shouldn't be anything to worry about.

The site below is a reptile forum and there is a water dragon section that is very helpful, you can ask and answer questions, talk among other water dragon owners and even compete in a water dragon photo contest so check it out become a member and come say hi!
http://www.repticzone.com/forums/WaterDragons/index.html

Good luck with your WD!