Yay! I can definitely speak out of experience here...well, a little, anyways. I had a pretty large pond deal in my gecko tank for a while, complete with water fall... Gollum LOVED it, in fact i think she is bitter now because i took it apart a year ago and never replaced it for her. She did end up IN the pond at least a couple of times, usually of her own will. She would stare at the water intently, maybe watching the movement of the ripples? and then POUNCE onto it and take a big bite, like she was attacking it! of course all she got was a mouth full of water and a bath, but she never hurt herself. The water was shallow enough that she could stick her head up and not be underwater. It was VERY amusing, i highly recommend giving your crested some sort of moving water...maybe they all won't love it as much as gollum, but you never know. she was one happy gecko. I don't know if she ever actually swam or could if she had to, but I don't doubt it. I hope that helps.