When you see your reflection, you're taken by surprise. Your face looks very different, your features are softer and you seem slimmer, shorter and less muscular. When you catch a glimpse of the male swimmers again, your eyes are drawn to their muscular, handsome bodies and the bulging packages between their legs. A moment later, you notice you've got a hard-on and your nipples are visible against the fabric of your top.
Before you can feel embarrassed, though, you notice how the fabric is changing shape. Your shirt seems to shorten until it leaves your midriff bare, and you notice your figure has slimmed. Suddenly you notice how your chest is swelling under the top, and the material has started to concentrate around two swelling mounds on your chest. The flesh on your upper body seems to be being drawn to your chest, and there's no mistaking that you're developing breasts. But they feel so warm and sensitive, and the thought of having them played with or sucked by someone is so good, that you're not uncomfortable with the changing, it just feels good.
Your shorts seem to transform similarly. They merge with your underwear and thin into a cute bikini bottom, the fabric concealing less and less of your crotch- but as it does, there seems to be less and less down there to conceal. Your penis shrinks as the fabric does, never being exposed to the air to protect your modesty, and your balls tuck inwards to form a flat camel toe which soon opens to form a vaginal slit. By the time you're wearing a feminine bikini, your body is perfectly feminine to match it.
You breathe heavily for a few moments as you come to your senses and notice your feminized body, experimentally touching your new breasts and curvy, soft figure. But then your eyes wander to the boys by the swimming pool, and you notice all of them had gotten hard now they'd noticed you changing. Seeing a row of hard, thick, virile cocks, your mind quickly gives in to your new feminine urges. Your female juices start to pool in your underwear and a hard nub between your legs feels sensitive (you realize that's your clit). Standing there, you wonder what to do with these handsome swimmer boys...