Once I recover from the shock of the freezing water, I relax a bit, close my eyes, and let out a little telepathic sigh as the individual cells in my tail draw in the saltwater like a sponge. I feel so free! It's like being back home in Pacifica, swimming with Carla beyond the reef.

Oh, Carla! I swallow the lump that forms in my throat. Poseidon's beard, I miss her so much. Now I have to live on land and sleep in a log cabin with Shelly Sharkweather, piles of pink fabric, and gallons of perfume. On the upside, the stench will probably ward off wild animal attacks.

I dive to the bottom of the bay and swim through a thick meadow of eelgrass. The soft, long, green, ribbon-like leaves sweep against my body, awakening every nerve ending. For some weird reason, I think about Pierce.

Pierce! Holy crab! I'm down here acting like a fingerling who's never left the lagoon when I have to get to that yacht before Shelly mauls Pierce, or Pierce munches on Shelly, or some combination of the two happens.

A horrible image of Pierce and Shelly making out in some gaudy, gold-trimmed, mirrored yacht bedroom flashes through my mind and makes me queasy. The vision is so vivid. It includes a zebra-skin rug (totally gross by the way), a scarlet bedspread, and a lavender-scented bubbling Jacuzzi. If you remember, I'm only one-eighth fairy, but sometimes my visions come true. Okay, maybe a vision came true only once, but that doesn't mean it can't happen again.

I tighten the straps on my backpack and blast into turboswim. I'm going so fast that even with my enhanced mermaid eyesight, I barely notice the oily shimmer floating in the eelgrass. But as the shimmer intensifies, I feel a prickling sensation on my skin, sort of like a mild jellyfish sting. I decelerate enough to notice that there is no marine life nearby. The eelgrass is thinning and brown, and the kelp is slimy and decomposing.

I like to think I'm the kind of mermaid who can appreciate many ocean decor—I mean, not every square inch can be a coral reef—but this place is totally unpleasant. It is unlike anything I've ever seen.

I turn around, and I'm about to shove off when a telepathic shriek explodes in my brain.

"Aaargh," I reply. Poseidon's beard, that screech is loud. It sounds like someone's in trouble. Will I ever get to the party? I look around for anyone else who might help, but nope, it's up to me. Great!

"Where are you?" I telepathically holler.

I get no answer besides more of the high-pitched, brain-scrambling noise. I clench my teeth and continue looking for the source. The screaming gets shriller, and the oil gets oozier. The scream intensifies. I see an enormous limestone rock jutting out from the floor of the bay.

"Can you please stop screeching and tell me where you are?"

The noise coalesces into words: "Stay away from the cave. Save yourself!"

"What cave?"

"Go away before it's too late!"

"I could get out of here a lot faster if you'd shut up and tell me where you are." I know I don't sound all that heroic and patient, but you really need the victim to at least try to help with the rescue at a time like this.

I flit around the limestone wall and see an eerie light emanating from a fissure in the rock. I peer inside and gasp.

The water inside the cave is a pulsing kaleidoscope of indigo, yellow, pink, chartreuse, orange, and teal. It is beautiful, but scary—like a jellyfish or a sea anemone or a stingray.

"You should go away, please," begs the voice.

This has to be the place. I strip off my backpack and try to squeeze through the fissure, scraping myself on the barnacles growing along the surface of the opening as I do. Now I'm bleeding. Terrific. The sharks won't be far off.

I finally make it through. The swirling colors inside the cavern, which is about the size of my cabin, are intense and disorienting. I can't breathe. It's like oxygen cannot exist in this place.

"Where are you?" I am not panicking. I am not panicking.

"In the cave!"

"I know that already." Okay, I'm panicking a little bit.

I catch a glimpse of a coral seahorse thrashing as if he's been struck by lightning. His tail is pinned under a boulder that must have dislodged and trapped him. I lunge toward him. I lift the boulder and throw it to the side. I try to grab the seahorse so we can get out of here, but he keeps wiggling out of my grasp.

"Can you settle down?"

"Nope," he says.

I finally manage to scoop him into my hand and cover him with my other hand. I jet outside the cave, scraping myself again. I don't slow down until I'm beyond the eelgrass, in clean oxygen-rich water, and the seahorse stops struggling and relaxes his cries into a tiny whimper.

I stop next to a healthy kelp bed to examine the damage to the seahorse and me. He seems fine, but I'm bleeding all over, and my hair is a disaster. Right then, a gang of great white sharks charges at us.

"Come on, guys, not again." I don't have time for this. These are the dumbest sharks ever. "Don't you remember me? It was only a week ago, for Poseidon's sake!"

They look stupidly at one another, and I can see it finally registering that I'm the one who flung them halfway to San Diego. They glance kind of longingly at the seahorse. "No way," I say. "You can't have him either. You do not understand what I've gone through to save him. Shoo!"

They turn around and swim off, allowing me to bleed in peace.

"Thank you," says the seahorse.

"You're welcome," I say. "Sorry about yelling at you before."

"I deserved it. But why did you come after me when I warned you to stay away?" He's floating above my palm now, looking a little stronger, but he's trying to look over my shoulders. I turn my head to see what's so interesting, but all I can see is kelp and more kelp.

"It sounded like you were hurt."

He looks at me with sad, tiny black eyes. "Few creatures would have come into that cave to save a seahorse."

"Stop looking around. The sharks aren't coming back." I hope.

"I'm not worried about sharks."

"Then what is it?"

"Nothing," he says, looking defensive.

"Right. Can you tell me why you ended up in that cave?"

"It seemed like a good idea at the time."

"The burning water wasn't a tip-off that maybe you were wrong?"

"Better to die in that cave than have Olga find me." He winces.

"Who's Olga?"

"My wife." He looks super anxious now.

"You were hiding from your wife?"

He stops acting like a wanted criminal and looks at me intently. "She wants more fry! I still haven't gotten my body back from the last brood. Females just don't understand what it's like to be pregnant. The distended abdomen! The weird cravings! The white pasty skin! If females had to carry the young, there would be a lot fewer seahorses. I can tell you that."

"Maybe, um, tell her how you feel? I'm sure she'll understand." I can't believe I'm down here dispensing marital advice to a seahorse. I've got my own problems.

"No, she won't. She's been acting crazy lately. A lot of folks down here aren't acting right. The sharks are even stupider than normal, as you just saw. Some of the jellyfish have started getting tangled in their own tentacles."

"What's wrong with the water?" I don't have time for this, but if something is wrong with the water, it could affect my entire family.

"Don't know."

"How long has it been like this?"

"I'm a seahorse," he says. "No sense of time. Look, I gotta find a new hiding place. If you swim across Olga, remember, you never saw me. And I guess I owe you for saving my life."

"It's okay; you don't owe me anything."

"If I live long enough, I promise to repay you. You're the nicest merperson I've ever met. What's your name?"

"Waverly."

"Thank you, Waverly." He bows. "I'm Beau, but if you see Olga, you never heard that name."

"Good luck." I wave goodbye. I'm pretty tired now, but nothing is going to stop me from getting to that party! I know I need to talk to my dad about what's going on in that cave, but it can wait a few more hours. I launch into turboswim.

The music is getting louder, and the yacht is slapping against the waves. I'm bobbing next to the stern, trying to figure out how to get aboard, when I realize I have bigger problems than scaling a giant yacht. I left my backpack with my dress next to that awful cave. There's no way I'm going back there, but I can't confront Shelly Sharkweather in front of the whole school naked. Plus, I'm bleeding, which is a very, very bad idea when you're going to a party with a sexy vampire, who may or may not have stood you up. Wait, did I just use the word sexy to describe Pierce?

"I think you did," comes a sexy—I mean not sexy—voice from somewhere on deck. So much for the promise not to read my mind!