While I applaud your concern, badgirl, I just wanted to say I've had lots of pet rats through the years (yes--those are rats, not well-fed mice) and that's exactly the kind of thing they'd find fun. Far from drowning, they're excellent and enthusiastic swimmers and quite the little thrill seekers. In the video, you can clearly see them jump off of the boards (not glued on) and run toward the camera with what looks to me like a "That was fun! Let's do it again!" attitude.