Your name is Billy Edward, you were 12 years old, and this was your first time at a waterpark with thousands of people you didn't know, who were in line to go down the biggest water slide the park has ever had while you were there. Luckily, the line wasn't that long, so you had minutes to kill while you were there.
While you waited about 5 minutes for the line to get shorter, you take a look at the pool as you notice the people diving from the highest water slide, and going down it, but discover something odd. Every time someone from the front of the line goes down the slide, you see them sprout gills on their necks, while at the same time they grew scales on their legs as they entered the water. As you got to the top of the slide, you spotted why the other patrons at the park were growing gills, and scales.