As he watched his newly buffed friends horse around in the pool, Ty was getting increasingly turned on... all of their hard bodies pressing against each other, muscles flexing and curving as they struggled for the nerf football they were tossing around. Every motion was causing Ty to become increasingly aroused.
But there was a problem --- Brian might be gay, but Hank, Paulie and Ian weren't (at least as far as Ty knew). It was frustrating to see four beautiful male specimens, and knowing that they probably wouldn't have anything to do with him.
Ty was agonizing over this when an inspiration struck him as he watched them splash back and forth in the water. He carefully observed each of his friends: Hank in his black speedo, Brian in his blue, Ian in the red and Paulie in the green. Slowly he began to alter each one of them. Without them noticing, each of their feet began to push out into fins. Scales in colors that matched their swimsuits began to appear on their hips and legs. One by one, their legs began to merge together...
Paulie's olive skin blended seemlessly with a luminescent green tail fin as he effortlessly glided past Ian for a touchdown. Ian, now bedecked in a glittering red tail, swam underwater to the other end of the pool to receive the "kickoff," not surfacing, since his newly formed gill slits allowed him to breathe freely.
Brian, his magnificent blue-gold tail glinting in the sunlight high fived Paulie and threw the ball high in the air. Hank, now sporting a svelte jet-black tail-fin, propelled himself high into the air with a dolphin-like leap.
All four newly formed mermen looked incredibly sexy in their new forms --- and none of them noticed the changes in the least. Ty made sure, even as he was transforming their speedos into leather thongs supporting a seashell to hide their genitals, that each of them thought of this form as completely natural. Each of them thought they were some sort of "were-mermen," who had the power to transform themselves into this sea-going form at will, their magic speedo transforming with them.
The best part for Ty was that, even though they might be straight on land, each of them believed that they, like all mermen, were gay. They would have no problems pleasuring each other like the good friends they were.
Hank, Paulie, Ian and Brian were continuing to horse around, but now the casual contact between their now extremely lithe bodies had an air of eroticism to it. Entwined tails led to obvious hard-ons, and more.
Ty was thinking that it might be time for a swim...