There once was a man who loved to swim. Whenever he could, he frolicked all day in the waves. When he was working, he pined for the siren song of the sea.

Luckily, the man had a lovely witch of a wife who could help him with his passion. She gave him a spell that granted him gills, with the warning that he must never use it for more than a sun's trek across the sky.

The first time the man spoke the spell, he very nearly forgot his wife's warning. The joy of being able to fully embrace his devotion for the depths, free from the fetters and failings of his human form was fabulous. But still he managed to pull himself away from the sea just as the sun slipped below the horizon.

Life went on like this for quite a while. The man's ardor for the tides only grew as he spent more and more time beneath the bounding main. Still he heeded his wife's caution, and emerged every night before sunset.

But, as inevitably as the rising of the moon, there came a day when the man did not return to the shore. It was a day unlike any other. For the first time in the man's memory, the sea was completely calm. Instead of the usual wild romp through the waves, the man floated along in blissful serenity, enjoying the ocean like he never had before. He was more tired than usual, thanks to the long sleepless night he had spent with his wife. Forgetting everything but the gentle caress of the water, he nodded off to sleep just as the last rays of the sun disappeared from the sky.

On the cliff overlooking the shore, the witch's face spread into a wide grin.

He awoke the next morning more refreshed than he'd ever been. Panic soon set in, however, as he realized that he had violated his wife's prohibition against spending more than a day in the briny deep. He'd never asked what exactly would happen if he did, somehow he'd always become distracted every time he thought about it.

But what exactly had happened to him? He was obviously still alive and breathing, so his gills couldn't have disappeared. As he pondered the mystery, he realized that his hands weren't sliding through the water as easily as they once were.

He looked at them, and to his delight he saw that they were now webbed! He spread his fingers wide and examined the blue green webbing now connecting them together. As he pushed off from the seabed to try them out, a similar feeling of resistance down below revealed that his toes were now webbed as well!

Forgetting all about his wife's warning, he cavorted through the sea, marveling at the speed at which he shot through the water. As the hours went by, he started to notice even more changes to his body. Beautifully soft and shiny scales formed on his hands and feet, then crawled up his arms and legs. Delicate fins sprouted from his wrists, and his feet elongated to better propel him through the water. The hair that had adorned his body vanished into the abyss, while the hair on his head grew long, fair, and sensuous.

Each change brought more and more joy to the transforming man. Though he realized that he was slowly losing his humanity, not a thought was spared to returning to the shore. Even when his limbs started to soften, and it became obvious he was shedding his masculinity as well as his humanity, he wasn't worried.

As the day wore on, the changes only accelerated. Streaks of blue-green shot through the man's gorgeous blonde locks, while his ears lengthened, becoming scaly and finlike. His hips widened and his waist cinched, while his chest swelled into a lovely pair of breasts. A tail emerged from his spine, growing longer and longer. His legs shrank down into finny flippers, perfect for maneuvering through the waters. His penis, long since freed from any confinement, shrank away into nothingness, to be replaced by soft feminine folds.

As the sun once again started to sink below the horizon, the man knew that his changes were complete. A glance at his reflection confirmed what he'd long suspected. She had become a mermaid! She smiled as she realized she’d started thinking of herself as a “she.” Girl, female, woman, lady, mermaid… they all sounded so wonderful in her head!

She idly wondered whether the spell had altered her thoughts to embrace her newly feminine form, or whether she’d always had the seed of womanhood deep inside of her, just waiting to sprout. She giggled to herself as she realized it didn’t matter. Everything about her, from the tips of her ears to the flukes of her long, sensuous tail felt absolutely perfect.

She thought back to her wife, waiting for her back at their house. Had she known all along what would happen to her if she'd spent too much time in the sea? It seemed likely. In fact, she could see the figure of a woman waiting for her on shore. Her wife had never done that before in all the years she'd been playing in the sea. With a powerful kick of her tail, she swam back towards the beach.

The witch composed her face into a sad smile as she waited for her lover. In no time at all, the mermaid was before the witch, a look of rapture on her face.

"Look what's happened to me! Isn't it wonderful?" the lovely new mermaid said.

"Oh my dear, I wish you had heeded my warning," the witch replied.

"What do you mean? I love this beautiful new body!"

"I'm glad, because you'll be wearing it for a while. Since you've transformed all the way, you can never become human again. You will be a sensual siren of the seas forevermore."

The mermaid's heart leapt. Truth be told, the thought that she'd have to return to the land, and return to being male, had filled her with a dread she had never felt before. To be a wild, free mermaid, dancing naked through the waves for the rest of her life filled her with joy beyond measure. But then another realization struck her.

"And... us?" the mermaid asked her wife.

"Oh, my sweet Lorelei," the witch said, giving the new maiden a name to match her form, "I'm afraid not. The spell that I gave you simply doesn't work on witches."

"Then I guess... this is goodbye," Lorelei said sadly. The new name her wife had given her sounded lovely to her ears, and she decided to keep it. "May I ask for one last kiss before we part?"

The witch was about to refuse, but something in Lorelei's voice made her yearn for the mermaid's lips upon hers. Lorelei took her wife's face in her hands and gave her the most erotic kiss she'd ever experienced in her long life. A minute later, the two broke apart, the witch looking red and flustered, while the mermaid smiled mischievously.

"Goodbye my love!" Lorelei said with a wave, before returning to the depths.

The witch stood at the water's edge for ten minutes, her mind consumed by the kiss she'd shared. Try as she might, she could not get it out of her head. She reached down to splash herself with some water in an attempt to restore some semblance of sanity. It didn't help, only causing an overpowering urge to tear off her clothes and throw herself into the sea after the mermaid.

Finally she managed to pull herself away, heading back up the cliff to the house. She had originally planned to stay there for a while and put her affairs in order, but now she thought it best to depart as quickly as possible.

As the witch turned to leave the cottage that she had shared so many blissful days and passionate nights with her former husband, she heard a sound rise up from the sea. It was a song, the clarion call of the siren. As it surged through her head, reverberating through her body and soul, she began to weep for the beauty of it. It took everything in her power not to jump off the cliff.

The witch had had many husbands over the centuries, each loved and discarded in their turn. When she had realized her latests love for the sea, she knew she had the perfect plan to part with him painlessly. She had, of course, long known of mermaids and the longing and allure they provoked in mortals. But in her hubris, she'd assumed she could never be seduced by one.

As the song slowly faded away, the enormity of her mistake dawned on her. Any thought of leaving was out of the question now; how could she part with something so beautiful? Consumed by lust, she sprinted back into the house, stripped off her clothes, and leapt on the bed. To her horror, when she imagined the strapping stevedores and comely courtesans that made her heart flutter, she found that they did nothing for her. All she could think about were the bare breasts and titillating tail of the naughty nymph she had so foolishly fashioned.

Even as she faded into sleep, the witch had no respite from the siren's song. The night was one long dream of wild, passionate sex with the mermaid. She woke up covered in sweat, and when she went to wash it away, the gentle caress of the water only reminded her of what now dwelt in the bay below.

She hoped against hope that her erstwhile paramour had moved on. But the next night, and the next, and the next, the mermaid called for her wife. Still the witch resisted, despite it being the hardest thing she had ever done. A year and a day the mermaid sang, despite the yearning in her heart to explore the vast ocean that was now her playground.

Then one night, as the full moon rose overhead, the witch realized that the mermaid's song hadn't appeared. Despair as she'd never felt before filled her heart. Tears flowed freely from her eyes as she sprinted down to the shore. She knelt down in the sand and slammed her fists into the surf, letting out a long wail of sorrow.

There was a giggle and a splash, and the witch looked up to see the mermaid swimming toward her. In that moment, the witch's heart finally surrendered. She realized that she'd been bested by the siren, completely and utterly. It didn't matter what came next.

Lorelei joyfully caught her wife in her arms as they kissed. The witch's clothes disappeared in a matter of moments. They made love for what seemed like hours. The witch hadn't been sure what to expect, would the mermaid drown her after they were finished? Would she leave her as the witch had intended originally?

When scales started to appear on the witch's body, she realized what Lorelei intended. She giggled as the change she had wrought in her beloved took hold in her. Her midnight black hair lengthened and streaked with blue, her breasts swelled, and she sprouted a tail to match the one that adorned her wife. She felt her witchhood fade away into nothingness, the magic she had cultivated carefully for so long disappearing into the abyss. Soon her form was a mirror of Lorelei's. They entwined their tails in a mermaid's embrace, floating delicately in the gentle waves.

"My sweet Calypso," Lorelei cooed. Calypso's heart fluttered when she heard it. The newly born siren took to her new name instantly.

"My lovely Lorelei," Calypso cooed back. The two mermaids, hand in webbed hand, swam out into the wide ocean. But legend has it that every year on a certain day, in a certain bay, a song can be heard that soothes the hearts of lovers, containing the promise of eternity.