Concerned about chinese water dragon behavior

I tend to my roommate and her brother's chinese water dragons while they are gone. Her brother usually comes once a week and puts them in the tub for a little bit. Today while they were in the tub he noticed my roommates water dragon became stiff, closed it's eyes, and stopped breathing. We removed it from the water and it remained that way and would only move when it was poked. It was like this for about 2 or 3 minutes then it went back to normal. Then we put it back in the tub with the other water dragon. After a few minutes it did the same thing but flipped over for a few seconds. We flipped it back over and it was fine. We decided it was time to put them back in their tank. The other water dragon was perfectly fine. This is the first time this has happened. I am very concerned about my roommates dragon. She loves it very much. I was wondering what this means or why it did this?

:confusd: :confusd: :confusd:

What temperature was the water?

oh sorry I didn't mention that to begin with. The water was about room temp. The dragon that reacted this way we have had since March and is older out of the two. We aren't sure of the genders yet.