Bastian laughed, poking fun at his girlfriend as he stretched his arms, warming up as he usually did before jumping into the pool. “You really think you can beat me, huh? You’re not exactly the next Phelps.”

“I never said that. I told you to stop making fun of me...” Bianca harrumphed, looking around at the other visitors to the public pool as she dipped her toe into the cool water.  “...other people are watching us.”

“Ha! You’ll never win because of your huge boobs getting in the way!” Bastian joked again, gesturing towards his own chest. “Not exactly hydrodynamic, are they? Men are naturally much better swimmers.”

Bianca was tired of her boyfriend’s constant teasing, so she decided to teach him a lesson he would never forget. Beginning the gestures of a spell, she shouted in anger. “I’ve had enough of your shit! Let’s see how you like it!” Her eyes suddenly glowed a bright orange, and suddenly Bastian felt a strange feeling in his body. Everybody else had stopped in time and the world was growing all around him. Reaching up to his face, he felt his features shift and morph, his hands becoming thinner and more delicate as his hair grew long and dark.

Now looking up to see his girlfriend, himself now at just 5 foot tall, he felt his entire body become more slender while his ass puffed out into a generous set of curves. “Wha-what are you doing to me?” he said in his now feminine, high-pitched voice, shocked at what was happening to him. As his cock sucked into his body and his boxers morphed into a skimpy two-piece bikini, his transformation into a full biological woman was complete.

“I’m just showing you what the struggle is like...” cooed Bianca, “Speaking of, you’re missing the most important part!” snapping her fingers her girlfriend’s chest ballooned out, his enormous boobs expanding into funbags the size of small watermelons.

“You’re turning me into a tiny slut! These boobs are bigger than my head! Please-” before he could beg for her forgiveness she pushed him into the water unexpectedly, causing him to yelp like some damsel.

“Now you can see what carrying around a pair of giant, ‘not-exactly-hydrodynamic’ boobs are like!” Bianca laughed, her eyes returning to normal as everyone around them resumed their activities. Pointing at his chest, she noted their buoyancy. “At least those enormous airbags will help you float!” Noting her boyfriend’s defeated look, she jumped in beside him. “I tell you what: I promise that if you beat me in a race, I’ll change you back. Now GO!” She kicked off, unceremoniously splashing water into his horrified face.

“W-wait! I wasn’t ready!”  Bastian called, floundering in the water to catch up, his bouncing breasts almost slapping him in the face. “These titties are so huge! They... they’re slipping out of my bikini! I don’t want people to see my nipples! I’ll never catch up! I don’t want to be stuck like this! Slow down!!!”