As soon as Billy came in the water he started changing just like you did a moment ago. His clothes also vanished when they made first contact with the water. So now, you can clearly watch your best friend getting older. It was kinda hypnotic to watch, so you didn't notice that he was actually drowning because he didn't sign any contract to get gills like you or your parents did.
His preteen body immediately hit puberty and his limbs stretched like they're made of rubber, closely followed by his hands and feet which ended up several sizes bigger than before. Your friend quickly got big feet like a pro swimmer and they were helping him to swim back to the surface. Meanwhile, his first signs of body hair started to be noticeable, particularly on his armpits and crotch.
When Billy reached the surface for the first time, he wasn't a 10 years old kid anymore. He looked more a teenager of 14 or 15 years old whose body was still disproportional and had room for more growth yet. You noticed that his balls had swelled a little or it seemed they had because they have finally dropped into a barely loose scrotum. His dick was long and thin like a pencil, but you weren't sure if they looked like that before.
However, you had little time to appreciate it because the former old man came out of the water and pull Bill down once again. They're fighting to stay at the surface and their movement was making a lot of foam that makes it difficult to see what's going on in there. Meanwhile, you could see your parents coming out from the water on the other edge of the aquarium, they're far from you but at least they are safe and apparently unchanged.
After almost a minute you watched the former old man coming out of the water once again, however he didn't look as young as a moment ago because he had aged at least 10 years older. He looked like a grown man but not as old as he was at the beginning. He started to swim to an edge of the aquarium when he was suddenly pulled down again. You assumed it was Billy who was trying to reach the safety before that man.
You expected to see the teenager you'd seen a moment ago, but you got a big surprise when someone else come out. Billy had grown a lot since the last time you watched it and now he looked like a full grown man, maybe around his thirty years old. Those awkward lanky limbs were a thing of the past because this Billy got meat on those bones.
His legs and arms were thick and strong, he had a wide back and an even wider chest that matched with his thick neck, prominent Adams apple and square face. All of that covered with a thick layer of hair that made him look like a wet bear. You was so curious to see if his private parts had also changed but there was so much foam to watch them.
You remembered that if Billy stayed too much time in there, he would get too old like you. So, you decided to jump in and help him. You have already reached the limit age so it won't affect you anymore. In less than a minute, you managed to take Billy off the water who laid on a bench nearby. Fortunately he didn't got any older, unfortunately he ended up around 20 years older than when he came in.
He was panting and trying to recover from the experience and you used that time to take a closer look at his newly grown manhood. The pencil look you watched a moment ago has turned into a fat salami that was so big that it fell to a side and it was dripping water to the ground. His scrotum was barely loose anymore, as it hung very loose now and it partially covered Billy's hole that now was pretty hairy and dark.
You felt tempted to touch it and when you did it, both you and Billy got a weird shock inside you that made your dicks sprung to life. It was they have a life of their own, you thought as it was the first time you watched an erection. Driving by your innocence, you made your dick tip touches Billy's and you noticed that he had some loose skin around his tip. You didn't know what a circumcision is, so you just assumed it was natural difference between you.
Billy moaned and started to drip precum from his mushroomy glans. He was so wet that you didn't notice it but you actually noticed that his balls were churning like they're waking up or something like that. You felt a tingle in your own balls as they started to churn too. You're going to squeeze them when you heard Billy moaning and you decided to squeeze his balls too. His were hairier than yours despite you're way more older than him.
You were wondering if all grownups had hairy bushes like you or Billy when one of his thick legs fell off the bench. It was quite hairy too and his feet had grown hair as well. You're hairy but not as hairy as Billy was now. So, in a rush of curiosity you took some hairs from his butt and suddenly pulled them out. He yelled in pain and immediately recovered his senses, not before he shot his first dose of cum to the world.
"What happened?" He asked with a very deep voice that even sounds manlier than your dad's. You realized that he was still dizzy as he kept a hand on his forehead. You noticed that he had a thick bush of hair on his armpit as well and a few seconds later you also shot your load. "I was drowning." He said between pants and you knew you have to explain him what's going on, or at least what you understand about it.