“What’s the difference?” Gemma asked.

“Well, for starters, mermaids don’t exist, and we do.” Penn smiled.

Thea rolled her eyes, then dove back underwater, presumably swimming off.

“I’ll explain it all to you later,” Penn said. “For now, why don’t you take your new body out for a swim? We’ll have plenty of time to talk when you’re done.”

“I…” Gemma wanted to know what she was, needed to know, really.

But she could feel her tail below her, swishing through the water. It felt powerful and fast, and it was almost itching to swim.

At least she knew part of the truth now. She knew what they were, and they weren’t going anywhere. Without saying anything more, Gemma dove under the water.

It was better than anything she’d ever imagined. She moved faster than she ever thought possible. She darted around the ocean floor and chased fish simply because she could. Outrunning a shark would be a cinch, and she almost hoped she found one so she could try.

It was the most amazing, exhilarating feeling she’d ever had. Her skin felt alive in ways she’d never known possible. Every move, every tremble, every change in the current rippled through her.

She swam as close to the bottom as she could get, then she raced up to the surface and leaped, flipping through the air like a dolphin.

“Easy, there,” Penn called. “We don’t need to draw attention to ourselves.”

Penn sat on the rocky shore of the cove. She’d pulled her tail out so it lay bent on the ground. Right in front of Gemma’s eyes, the scales rippled, shifting from iridescent green to the golden tan of Penn’s skin. It split into two legs, and Penn stood up. She was completely nude from the waist down, and Gemma quickly averted her eyes.

“Don’t be shy.” Penn laughed.

She walked away and dug around in a bag that sat by one of the cove walls. From the corner of her eye, Gemma saw Penn pull on a pair of panties and a sundress.

“We have clothes in here for you, too,” Lexi said as she pulled herself out of the water. “You don’t need to worry.”

Thea got out after Lexi, and Gemma waited until all three of them were dressed before she swam over and pulled herself out. She scooted backward up onto the shore, so the rocks scraped her fins. She pulled her tail out, and it flopped on land for a few seconds before the familiar flutter ran through them.

As her tail began to transform back into human legs, she ran her hands over it. She could actually feel the scales shifting beneath her fingertips.

“That’s incredible,” Gemma breathed, staring in awe at her skin. “How is this possible?”

“It’s the salt water,” Thea answered and threw a sundress at her.

Gemma caught it and stood up. She half expected her legs to collapse back into a tail beneath her, but they stood strong. Hurriedly, she pulled the dress over her head, putting it on over her tank top, and kicking off her torn up shorts.

“Well, it’s not just the salt,” Penn corrected her. “You can add salt to freshwater, but it won’t really work. It’s the sea. You may feel hints of it in ordinary water, but you won’t transform unless you’re in the ocean.”

“But … what if I hadn’t transformed?” Gemma asked. “I would’ve died if I hadn’t turned into a siren.”

“You’re fine now,” Thea said. She crouched down in the center of the cove and began building a fire.

“Of course, it hurts when you do a back-flop into the ocean.” Lexi giggled. “You’re supposed to dive, silly.”

“I didn’t know that, since you pushed me.” Gemma glared at Penn. “Why didn’t you just tell me what was going on?”

“That would spoil all the fun.” Penn winked at her, as if she were referring to a private joke instead of Gemma’s near-death.

The fire Thea had been working on suddenly roared into life, filling the dark cove with warm light. Penn sat close to the flames, stretching out her long legs and leaning back on her arms. Lexi sat next to her while Thea seemed content to kneel in front of the pit, stoking the fire.

“You did this to me,” Gemma said, but she wasn’t accusatory. She wasn’t sure what exactly they had done to her, so she couldn’t tell if it was a gift or a curse. So far, it felt a lot like a gift, but she still didn’t trust Penn. “You turned me into this siren or whatever. Why?”

“Well, that’s the crux of the matter, isn’t it?” Penn smiled.

“Why don’t you have a seat?” Lexi patted the ground next to her. “It’s a rather long story.”

Gemma stayed where she was, standing by the mouth of the cove. The waves from the bay lapped against the shore, and the engines of boats hummed in the distance. She glanced out at the night, already longing to get back into the ocean.

The last time she’d been out here, Penn had nearly killed her, and it was only a few minutes ago that Penn had pushed her off the top of a cliff. It was hard to juxtapose that with the knowledge that they had given her the most wonderful, exhilarating experience of her life.

Swimming as a siren had been by far the most glorious feeling she’d ever experienced. Even as she stood there, arms crossed over her chest and seawater dripping off her skin, she wanted to get back in the water.

It took all Gemma’s energy to force herself to stay on the shore, to hear what they had to tell her. But she couldn’t bring herself to step in closer to move farther away from the water that seemed to sing to her.

“Suit yourself.” Lexi shrugged when Gemma refused to move.

“It is actually quite a long story,” Penn said. “It goes back to when the world was young, when gods and goddesses still lived freely among the mortals.”

“Gods and goddesses?” Gemma raised an eyebrow.

“You’re skeptical?” Thea laughed, a dry, bitter sound that echoed off the walls. “Your legs just transformed into fins, and you’re skeptical?”

Gemma lowered her eyes but said nothing. Thea had a point. After everything she’d seen and felt the last couple of days, she would believe anything they told her. She had no choice, really. Any answer would have to be beyond her scope of reasoning to explain the supernatural things that were happening.

“The gods often lived here on earth, sometimes helping the humans with their lives or merely watching their joys and sorrows for their own amusement,” Penn went on. “Achelous was one such god. He ruled over all the freshwater, nourishing all life on Earth. Gods were the rock stars of their times, and they often had many lovers. Achelous was involved with many of the muses.”