Like everyone else said, you don't have anything to worry about. I feel bad for saying this, but I actually started laughing at the image of him falling in his water bowl upside down, even though I know if I was in your shoes I would have been freaking out too. The first month whenever I would put Orochimaru back in his tank he would stay frozen in whatever position I set him down, which was sometimes awkward and hurried because I was also afraid he would bite me again. I think they do that when they're unsure if everything is safe or not. After a few seconds or minutes they start moving again. As for getting bit, I promise it doesn't hurt at all, its more surprising than anything and happens so fast. You'll learn his body language, an S shaped neck is a good sign that he's looking to strike. Also, my snake just grabbed his mouse and plopped into the water bowl with mouse and all, he stayed coiled and killed it. The water doesn't seem to bother him, I actually saw a cool video on here of a BP swimming in a fish tank of his own volition!