Excited you blurt out "I want a fishtail that I can flop around!" The nurse chuckles at your enthusiasm and says "certainly, step this way..." You follow her into a well-lit backroom with an examination table and a large device which looks like some sort of laser cannon. "Take place on the table", the nurse says, "while I ready the transmutator" and she pulls the mechanical arm of the device over to the table. She starts tapping on a console and pulls a switch, lighting up the tip of the device which now produces a light humming sound. The radiation makes your body feel warm, and you watch your leg skin flake into an infinity of tiny scales, colored in various tints of blue, green and gray. Your body melts from the crotch and you can see your legs quickly fusing together into one large mass, with big bony fins growing from the end and near the top of your fish flesh, a small sheath beneath the scales that reveals where your genitals had gone. The nurse shuts down the machine, helps you off the table and asks you:"So...do you have any sort of transport handy to help you move, 'cause your legs aren't exactly functional anymore..." She's right. You now have the fishtail you wanted, but how are you gonna move with this thing?