you strip down into shorts, and jump into the pool, the water is refreshingly cool, and you go sit on the steps out of the pool, and rest.
you wake up a couple hours later, and when you try to put your shirt on, something feels funny, but you dismiss it as a breeze. You notice a sign that says no swimming. You wonder, why would there be a no swimming sign at a pool?
as you walk down the street, people are giving you funny looks, but you figured they were just wondering why you were so wet.
when you get home, you daughter runs up to you and yells "cool costume!"
you look down at yourself, and realize why people were looking at you, and why there was a no swimming sign, and you run to the bath room to see what else has changed other than your hands.
you take off your shirt, and see webbed hands, and you are covered in light-blue-grayish scales. you look in the mirror, and see your face looks more like a fish, and you passed out in terror, seeing your tail just before you fell to the floor.