As you turned towards where the shout had come from, you realized two things. One, it had been Maddie's voice, that same sing-song, accented twang that made you shiver just from a single word. Two, you realized that you heard hooves clattering against the ground, leading you to assume that she must have been riding a horse or something. The last conclusion you would've expected to come to was that the horse and maddie were one in the same - and yet, as you turned around, your jaw dropped at the revelation.
She was still wearing her hat, still donned in a 'shirt' that barely served to keep her incredible bust pushed up. Her arms and abs, delightfully muscular, still glistened in the sun, and she still towered over you. But right at the waist, where there ought to have been her long, powerful legs, there were... well there were legs alright. And fur. And hooves. From the waist down, Maddie was a centaur - not the size of a full adult horse, closer to human-sized, but still larger and taller than any normal human being.
You stared in slack-jawed amazement as she approached, a hand instinctually reaching out to feel her soft black fur once she was close enough. You could feel the sheer power in those legs, the raw, natural might of her equine lower half. Looking up, your eyes met hers, that smirk making your heart skip a beat. "Y'know, I knew y'all's was special the moment I laid eyes on ya." One hand on her hip, the other reaches down to grasp yours, giving it a gentle squeeze as she leads out into a field.
"Y'see, them waters, they make ya mighty strong - because after a while, y'all ain't entirely human no more." She whistled sharply, and from a far-off barn, you could see several figures emerging. Human up top, horse down below - more centaurs, and they look to be girls. The farmhands. "Lotta girls don't take too kindly to the water, and that's alright, but you... shoot, I ain't never seen nobody take to it so quick!" Her hand squeezes yours again. "Truth be told, I was kinda thinkin' - kinda hopin' too - y'all would spring a tail right then and there!"
No wonder that creek felt almost magical - it was magical. "You mean, that water... if I'm in it or drink it long enough... I'll become... like you?"
"If'n you want to, of course. Now I know, big and scary life change - I was the same way. But think about it!" She stopped, leaning down to pick up your other hand and hold it gingerly. "Y'all'll spend the rest of your life fit as a fiddle, beautiful, powerful... and bein' like this, with all yer legs out, just enjoyin' nature, runnin' wild..." She sighed. "I reckon there ain't but a few things in this whole world feel better. How about I give y'all a ride - let ya feel it yerself, see what I mean?"
You were in a daze, trying to comprehend all of this, but too head over heels for this bombshell redneck to refuse. You noded, and she quickly pulled you up onto her back, your chest right up against her back. She purposefully move your hands to rest on her enormous mounds, calling it the best way to get a grip, before taking off into a gallop. You squeezed tight on her breats, partly because you didn't want to fall off, and partly because the little moans she makes drove you crazy like nothing in your life ever has.
She's right about the feeling - it's incredible. The wind blowing through your hair, the sun on your skin, the feeling of freedom in a wide open field as your combination steed and crush tears around - nothing in your old city life could possibly compare to this. You could scarcely believe this was happening, and yet here it was - this gorgeous centaur was offering you a chance to be as breathtaking as she was. The thought of your wimpy body transformed into that of an amazonian goddess had you delirious with lust; all you had to decide was whether or not it was worth becoming something not quite human.