Written for the sam-centric h/c fic challenge over at the Oh!Sam livejournal community.

Prompt: Sam is attacked and captured by the Baddie of the Week, which happens to be some sort of aquatic or amphibious beastie. The creature drags Sam to its seaside lair in a cave and immobilizes him there, cold, wet, and injured.

Naturally Dean tracks him down, but by the time he finds Sam the tide is coming in and their escape from the cave is underwater. Sam is too weak/injured/cold to be able to swim out, so they are forced to spend the night in the cave. Dean cuddles Sam to keep him warm, talking to him through the night to keep him awake and grounded.

This is also for KKBELVIS who has nearly drowned Sammy spectacularly several times. If you haven't already, you should check out her stories.

Same disclaimer as always: Nada

Fishing for Mermaids

Small waves lapped lazily against the little rowboat, rocking them gently. Dean dipped the oar into the water, pulling slightly to keep the boat's nose pointed toward the craggy cliff rising at least twenty feet above them. The rock wall tapered into jagged arms that protected the small half-moon bay from the harsh winds that whipped over the open ocean, so within Bottle Bay the water was tranquil, smooth, a favorite spot for fisherman, and only accessible by boat. Unless you were stupid enough to jump in, Dean thought as he gazed up at the top of the highest rise. Of course you'd have a long swim back around to the tapered arms to find a place to climb back out.

It was beautiful here, peaceful. Sunlight glimmered across the green water. A perfect day for a fishing trip with his brother, except they weren't exactly out here to catch fish.

"Mermaids." Shaking his head for about the hundredth time, Dean grinned.

Straddling the other crossbench sideways, Sam looked up from the hand-held fish sounder, white teeth flashing. "You're picturing Daryl Hannah again, aren't you?"

"Only kind of mermaid I want to tangle with. Blond and busty."

"Until blond and busty cracks your chest open and chows down. You know-"

"I know we're not hunting a Disney character," Dean interrupted before Sam could go all encyclopedic on him, spouting about all cultures having some fable of water demon from Aboriginal bunyips to the Maltese Sirena and everything in between like krakens and selkies and grindylows. He heard it the first time when greek boy said the myths probably all sprang from a common source anyway.

Dean adamantly kept calling them mermaids while Sam settled on calling them Nereids, since that's what Dad had called the water creatures attacking the little bay in his journal.

"Anything?" They'd floated into the shade of the rock wall and Dean readied the oar to push them back before the boat bumped against it. A grey lizard scrambled up the rock, diving beneath a clump of weeds growing between a small fissure.

"Actually, I'm getting something." Sam stared hard at the depth finder. "There's a lot of movement just over there." Sam pointed. "Where the wall takes a sudden dip."

Dean twisted around on his crossbench. "Where that little hollow meets the water line?"

"Yeah. Could be the top of an underwater cavern."

"That'd fit with Dad's description," Dean agreed and started rowing that way. "Ya know what I don't get. If Dad took care of these things a decade ago, how come they are just now cropping up again?" More than six fishermen and swimmers had gone missing in the past couple of weeks. The coastguard was out looking for a rogue shark.

Sam shrugged. "Could be a weird hatching pattern, ten year cycle. We know Dad took care of the creatures, but what if he missed the eggs and they've been incubating this whole time . . ."

"Now they've hatched and they're hungry," Dean finished.

"Probably hatched a while ago, swimming around like little tadpoles, eating fish . . ."

"Until they grew large enough to take on something bigger . . . like people." Dean brought the rowboat right up to the little depression in the rock and peered inside the dark recess. "Good news is pretty much anything will kill them." He grinned, lifting a grenade in one hand and a machete in the other. "Slash 'em or blast 'em?"

Sam's mouth pulled down into the equivalent of a facial shrug. "Blast, Dean. Find the caverns they use, toss the grenades in. We just gotta find them first."

"Huh." The machine in Sam's hand was bleeping. "I think this is our cavern 'cause we got several hot blips that look to be just under that wall. He shoved the fish locator down into the bag by his foot and grabbed up a long bladed knife and a smaller bag of grenades. "Think the boat will clear the cave?"

Dean rested the machete along one oar and started rowing into the horizontal slash. "Boat'll clear. You, we'll just have to see."

Dean had been kidding until he had to crouch way over the oars once they entered the cavern. Glancing over he saw that Sam had lowered to the bottom of the boat, bending almost in two. They floated past the ceiling just over their heads. The daylight outside filtered at the mouth, casting the slanted walls and water in a muted glow.

"How far do you think this goes in?"

"Hopefully not far." Sam dug through the pack, setting aside the divers mesh bag with the grenades, and clicked on the flashlight before he even pulled it out. The beam cut through the darkness ahead of them. "Looks like it opens up."

The splash of the oars resounded around the rock interior as Dean pulled through the water.

"Wow."

Dean turned to look at what caught Sam's attention. They were coming into a larger cavern. Both boys straightened as they floated into it. There were several small ledges, like steps, with large gooey-looking gelatinous ovals perched on them. When the flashlight beam hit them, Dean could clearly make out moving forms inside, each about as large and thin as a greyhound. If the babies were this size, how large were the full grown mermaids?

"Let's blast them."

"Kay, yeah." Sam blew out a breath. "Dean, look some have broken through, hatched."

"We know that." Dean pulled the boat right up to the ledge. "Oh, good point. We count those and we'll know how many full growns we have to gank. How many caves you say there were?"

"According to the geological maps, three more." Long knife in hand, Sam stepped onto the slippery ledge right between two of the eggs. They came up to his thighs. "We'll have to check each cave." He looked down at Dean, holding the boat to the ledge. "Maybe we better try this the quiet way so we don't alert the grown-ups until the last cave."

"Slashing it is." Dean frowned. "There's nothing to tie off too."

Sam smiled. "Guess you get to be the getaway driver."

"No," Dean groused. He wanted to kill some water creatures. "You hold the boat."

"That's stupid. I'm already out." Even with only the light from the flashlight, Dean could see Sam's dimples had come out as his brother pressed his lips together, biting off a laugh.

"Fine." Dean caught the flashlight Sam tossed to him. "But the rest of the caves are all mine. Your lame ass can sit and wait in the boat like a . . . like a . . . lame ass."

Sam did laugh at that. "Fine." Dean cast the flashlight beam over his brother as Sam climbed the step-like ledges to the top. "Five."

"What?"

"Five. Only five eggs have been broken through. Eleven still intact."

That was good. Unless they found more hatched eggs in the other caverns, that meant there was only a fistful of grown mermaids they'd have to locate and kill. "I'm gonna take care of these I can reach," Dean set the flashlight down and lifted his machete, shifting his weight as the boat dipped. "Ready?"

"Go!" Sam yelled and Dean slammed the machete straight into the egg. The jelly substance gave easily until the blade met resistance. As the liquid slurped away, Dean stared into a surprised and hideously ugly face. Two large fins quivered back and forth like Dumbo's ears, sprouting from an almost skeletal head with long stiletto teeth cramped within a circular lipless mouth. Gelatin slop sloshed off the body. No way was he calling these things mermaids anymore. They didn't even have breasts. For good measure he slashed off the head, pulling the boat forward to take out the next one.

He heard Sam's grunts and the hissy gurgle of the eggs being split open as his sibling worked higher up. As Dean dispatched his third egg, a piercing shriek shrilled out followed with Sammy's shout of "shit!"

One of the Nereids had come out of its egg swinging. Clawed fingers scrambled across Sammy's chest, the webbing between finger bones splayed like Japanese fans. The tail was wriggling and slapping the rocky floor as the beastie used its claws to climb up the kid. Sam clambered backwards, smashing onto more eggs as he tried to get to his knife that must have been thrown back out of his reach.

Sonofabitch. Dean jumped out of the boat, boots squishing through the ruined eggs, keeping the boat's rope in his fist. "Sam!"

"I'm good. Don't lose the boat!" To prove his point Sam's fingers curled around the hilt of his blade and he swung it across his body, wedging it into the Nereid's side and swiped it off his torso like a Frisbee. It slammed into an egg to Dean's right and the hunter rammed his machete down, stabbing two Nereids at once. Couldn't help the satisfying grin from popping out over that one until he heard the deep intake of breath from his brother.

Dean twisted around quickly. He knew the subtle differences in all of Sam's noises from exasperated sighs, sleepy gasps, annoyed huffs, angry snorts or suppressed sniffs. The next shuddering exhalation spoke of pain.

"Sam, what's wrong?"

Sam's head snapped up, his forehead furrowed with deep horseshoe creases. He pulled a bloody hand away from his chest. "I'm okay. Just a bite."

"It bit you? I'm coming up."

"Just hang onto the boat. Let's finish th—Dean, behind you!"

Dean swung around, coming face to face with an inverted vee nostril and scissoring teeth. Even though the chest looked emaciated, scaly skin stretched tight over ribs, the bitch was huge. Holding herself out of the water with her arms on the ledge, her upper body alone was easily the same height as Dean.

Dean took that all in within a second. The same second he swung the machete and heard Sam shouting for him, boots slapping stone. The same second the monster leaped forward into Dean, grabbing him around the waist and slipping backward into the water. Sam's shouts were instantly cut off as Dean entered a world of dark silence.

He'd lost the machete in the fall. Water pulsed along his skin as the creature let them descend toward the bottom of the cave. Dean couldn't see a thing, just felt the steely arms pinning his arms to his chest and the pressure to take a breath building in his lungs. Hell with that. He kicked hard, connecting with solid muscle. Tail? Whatever. He kicked again, again. The arms loosened a fraction. Damn. All the bitch had to do was hold him down here. He'd drown soon enough. These Nereids drowned their prey like a freakin alligator.

He kicked again, again. Slammed his fists back. He wouldn't go easy. Suddenly the Nereid jerked, the arms lost their hold and Dean floated free. He scrambled upward, nearly out of air when he realized he saw light just below him.

Shit! There was his brother, flashlight in his teeth, fighting with the Nereid. Dean could barely make out the oval of Sam's face, hair floating around him, glints of the long knife as parts of it moved in and out of the light. Shit! Shit! Dammit, Sam! Dean couldn't hold his breath anymore, he couldn't help Sam. Decision made, Dean swam to the surface, determined to get there, take a breath and arrow back down to help his brother.

He pulled through the water harder than he'd ever stroked before and exploded through the surface in a matter of seconds. He hadn't been as far down as he'd thought.

He took in several breaths and then one long one and dove under. He nearly choked out all his air when a hand clamped around his ankle. Light. Sammy's face. Dean's muscles tightened, pushing more air out of his chest. He twisted in the water, clamping onto Sam's arm and propelling him upward. They swam hard, crashing to the surface together, dragging in huge inhalations.

Finally Dean asked, "You okay?"

Still catching his breath, Sam merely nodded.

"What about the fugly?"

Sam pushed through a long exhalation and passed a flat hand across his throat in a slicing motion.

Dean grabbed both of Sam's shoulders, shaking him slightly. "Dude, you were full on Aquaman!"

"Well . . ." Sam drew in another breath, but at least he was talking. ". . . had to save Lois Lane."

"Superman's chick, dumbtard. Get your superheroes right."

Sam gave him the I-don't-care grin. "Dean, there's four more. We need to get out of the water."

"Don't have to tell me twice." They swam the few yards over to the boat that was floating free in the middle of the cavern and before Dean could say anything, Sam was hoisting him up. "Whoa there, cowboy." His stomach scraped across the side. "Ow, easy." As soon as he was in, Dean swung around and lowered the curve of his elbow to his brother. Looping his own arm around it, locking elbows for better grip and pulling ability, Dean hauled Sam into the boat. Normally his brother was heavy, but soaking wet he was a dragging weight. Sam got one long leg over the side and Dean hauled him in the rest of the way. The rowboat rolled the other way almost spilling them over the side before they leaned back the other way to right it.

Sam immediately grimaced and clutched his stomach.

"Let me see."

Sam's gaze flicked up from beneath wet bangs, but knowing it was useless to fight about it, he pulled his wet T-shirt up. Tiny red puncture wounds formed a crooked circle on the side of Sam's stomach. "They're not even that deep. I'm okay. Let's just get this done."

Dean frowned. "Okay, but the first thing we do when we're back at the Impala is disinfect that." He cocked his chin toward the ledge. "How many eggs left?"

"Only a few. Blast 'em?"

"Well, they know we're here. Might as well make a party out of it." Dean pulled out a grenade, slipped his finger in the ring. "Ready?"

Sam took up the oars and shrugged.

Grinning, Dean pulled the ring and threw the grenade. It arched over the water, grazing the top of the cavern and bounced onto the middle ledge. Sam was already pulling the oars toward the entrance.

"Down, Sam!" Dean's shout was lost in the blast's concussion, but Sam ducked anyway at the same moment they guided into the long entrance with the low ceiling. The water rolled in waves from the explosion, lifting the boat. The brothers leaped forward into the thin hull, half on and off each other as the boat smacked against the ceiling then dropped again. They stayed low until the waves stopped and the top edges of the battered boat stopped scraping the low rock.

"Damn." Staying low Dean simply started pulling them forward by pushing against the ceiling. "That sucked."

Which made Sam start chuckling. "This is the stupidest case we've been on. Mermaids."

"Nereids, Sammy."

Sam full on laughed at that. The sound echoed around the rock, making Dean join him. They were laughing hysterically when they floated out of the cavern's mouth and into the shade of the cliff.

Still chuckling, Dean unzipped the long waterproof case and pulled out a rifle. "Kay, we're gonna do this quick. Toss the grenades in each cavern and when the grown ups surface to play, we shoot straight into their gullets. Like fish in a barrel."

"Best plan I've heard all day."

"So where are the other caves?"

Sam pointed not too far from where they just exited. "There, there and there." Close together. That makes things easier. Sam rowed them over to the nearest cave. It was really more of a large scoop in the cliff face, high enough to oar the boat right into and look around. There weren't any rocky shelves in this one, no eggs, hatched or otherwise.

Sam rowed them back out into the sunshine. "Hopefully, the other two caves will be just as empty," Dean said.

"That'd be a nice change," Sam muttered.

The change in tone had Dean's head snapping up. "You okay?"

"Yeah," Sam said and then thought better of it. "No. These scratches are starting to burn a little. Probably the salt water?" Sam tried for a hopeful expression that failed miserably.

"That's it. We're done for the day."

"But the caves are right there."

"Be there tomorrow too." Dean shifted off his seat. "Pass me the oars."

Sam's mouth stretched and tightened while his forehead creased in resigned frustration, but he stretched an oar out at the same moment his end of the boat lifted then slammed back into the water with a huge splash. Already halfway off his seat, Dean tumbled over the side. His brother's shout was immediately cut off as Dean plunged into the water.

Two of the creatures were on him in an instant. Visibility was poor, maybe ten feet at best, but he could still see how ugly the bitches were, all teeth and rubbery scaly skin. Webbed hands dragged across his arms and chest, but he still had the rifle and fired point blank in a white skeletal chest. Water pulsed like arrows from the bullet. Yellow eyes stared at him as black tar-like crap exploded from the bullet hole, swirling in the water like melted wax in a lava lamp.

The hands fell away and the creature floated off, but the other hung on, claw-like ends of the fingers tearing into his shirts. Dean tried to bring the rifle around, even knowing it might not work again underwater, but he could still use the butt like a club, all the while he kicked and tried to swim up. He could see the bottom of the boat.

Stroking upward, the rifle was wrenched from his grasp. Dean looked down and found himself face to face with yet another creature. Freakin mermaid was locked onto his arm like a vise and both girls were pulling him down while he tried to go up. His chest spasmed in pain. The urge to open his mouth and gulp in a breath was damn near hard to ignore.

Suddenly Sam burst into view, strong strokes propelling him closer, hair streaming back, a third Nereid right behind him, reaching for his brother's calves. But whether the kid knew one of the skank's was behind him, Dean would never know because Sam surged right for him. A blade glinted in the green-tinged water as it arced past Dean's face and down into the shoulder of the Nereid clamped around Dean's right arm. She and Sam jerked away in a snarl of legs and muscled thrashing mermaid tail.

Dean rammed his elbow down on the other bitch and kicked away. He couldn't breathe couldn't breathe couldn't breathe. His lungs were clenching. Involuntarily he was going to suck in water any second now. He couldn't stop his chest from squeezing, even as his head screamed that he had to swim upward. But he couldn't leave Sam.

It was stupid, he knew, but he'd never been smart when it came to Sam needing him. His lungs hurt so bad. Nononono, calm down, go get Sam. But Sam was suddenly there, swimming parallel to him. Dean turned, kicking to the surface, bursting into light, struggling, gasping in oxygen so heavily he thought he might pass out.

Sam broke through the surface several feet away, flinging up water like a fountain.

Dean started swimming toward him.

"Get in the boat! They're coming!" Sam's whipped around, looking for the rowboat. It floated several yards behind him. "Dean, they're com-" Sam was jerked under the water just like the girl in Jaws.

Diving under, Dean swam after him. Dammit. The three remaining Nereids had Sam, one locked onto his stomach, the others fighting his arms and legs as they pushed him backwards through the water. Though the kid put up a good fight, their superior swimming abilities and muscular pumping tails carried Sam farther and farther away. Getting one hand free, Sam reached over a bony shoulder, arm outstretched for Dean before he disappeared within the murk.