A sharp pain in your tail, has you doubled over and clutching your sides. You bite your lip, and squeeze your eyes shut. The pain seems to be subsiding, but your tail feels so hot. Like someone just put you over an open flame. You open your eyes to see your tail splitting in two. You watch, hoping your legs are returning.
Sure enough, they are. Slowly, the scales recede until only soft human flesh remains. The slit that hides your cock and balls parts, and then retracts back into a foreskin. Your cock however, appear much larger than normal. About half the size of your weird fish-cock, it's about a foot long. As the scales disappear, you find that your legs are oddly hairless, and very smooth. And your muscles are more pronounced. The fluke at the end of your tail parts, and develops creases at the end. They gradually form ten independent digits, your toes.
A sharp pain at your sides tell you your gills are disappearing. You touch one as it retreats back into your sides. The slits are sucked right into the small creases between your ribs. The webbing between your fingers shrinks away to nothing as well.
As the transformation comes to and end, you find yourself staring at your body. You look like an Olympic swimmer, well developed muscles and long legs. Standing, you climb out of the bathtub and try to make sense of what just happened to you. You saw mermaids at the beach, fell into a pool of water, went home and grew a tail, masturbated with a strange penis, and then regrew your legs. Walking past the bathroom mirror you get one last shock. Your previously dark brown hair is now an almost honey blonde color. Running your hand through it, you determine it's also softer.
"Not your average Friday afternoon, that's for sure." you think. You rush into your bedroom to put some clothes on, and then head back to the beach. Surely the answers you're looking for are there. That's where this all started.
As you're dressing, you confirm your body has gotten bigger. None of your clothes fit right. Your shirts are stretched tight over your muscular chest and biceps, and your underwear are bulging, barely able to contain your package. Thankfully your jeans are still loose enough that they hide some of the obvious mound in your crotch. But your shoes are at least two sizes two small, forcing you to wear flip flops with your heels hanging off the ends. It's better than going barefoot, as that would raise more than a few eyebrows.