For Dean, being tossed around by a skinwalker bear is all in a day's work. It stops being so routine when he's thrown out onto a snow-covered pond with enough force to break through the thin layer of ice and plunge into the bitterly cold water beneath.
Sam doesn't dare take his eyes off the bear. He squeezes the trigger three times, finally striking the heart. Probably striking the heart, the stupid thing falls over and stops hitting people, anyway.
Giving the monster no further thought, Sam sprints toward the ice. A moment before he steps off the bank, his brain kicks in.
A thin-ice rescue is the most dangerous kind, more dangerous even than trying to rescue a panicked drowning swimmer. You try to walk out there, you break the ice and wind up in the drink with him.
Dean has managed to right himself, and he's clinging to the edge of the hole. He's breathing, which means Sam has enough time to try not to be stupid.
Sam runs back to the trunk, grabs a rope, and secures it to a solid tree near the pond. Then he breaks a couple low-hanging limbs, spreads them out over the water, and lays across them on his belly. Like giant snowshoes, they spread out his weight and protect the ice from cracking.
Much, much too slowly, Sam creeps across the ice on his belly. "Hang on, Dean," he calls, but his brother seems not to hear.
He can't afford to count on Dean's help with this one. It's not how fast the cold water will kill you, it's how unbelievably fast the hypothermia makes you stupid, clumsy and unable to help yourself, especially when you fall in dressed in nothing but a couple layers of cotton. A moment before Sam reaches him, Dean gives up his grip on the ice shelf and slips under the water.
Pulse pounding with eagerness, Sam still doesn't dare to rush. He creeps up on the hole, avoiding the area Dean had been clinging to, because that ice is probably already weakened. He ties the rope around his chest, leaving only a little slack between himself and the tree, and peers into the hole. There! A bit of Dean's jacket. Sam reaches out and grabs it. He pulls up slightly, and an arm drifts into view. Still moving gingerly, Sam grabs the arm. Finally, he can get his hands under Dean's arms and pull up properly.
Sam has next to no leverage lying on the ice, and Dean's sodden clothing probably adds twenty pounds. When Sam extracts him, it's less of a neat lift and more a matter of pulling a few inches, getting a better grip, wiggling back and pulling again, but finally Dean is lying beside him in the clean, crisp, freezing air.
Still sprawled out across the ice, Sam checks the pulse at his brother's wrist. Nothing. His brain gets in perhaps three syllables of panicked babbling before memory cuts in-the radial pulse usually disappears when the body temperature drops. Instead, Sam reaches for the carotid. It's agonizingly slow, perhaps one beat of Dean's heart for every five of Sam's. Given Sam's own level of fear and exertion, Dean's heart is probably beating fast enough for the moment. It's a lot harder to tell for sure whether he's breathing, and Sam decides to hold off on checking that until they're on firmer ground.
The real problem now isn't frostbite. Dean's skin is alarmingly white, but he simply hasn't been exposed long enough for deep tissue damage, and as long as he's thawed carefully, the skin should heal in time. Sam's not even really worried about the effects of oxygen deprivation, because the cold should prevent brain damage for some time yet.
No, with Dean out of the water, the biggest danger is cardiac arrhythmia, brought on by the sudden and drastic drop in Dean's body temperature.
Sam stuffed the dead rawhead into a closet and called 911. He didn't, couldn't can't care what would happen if the police found it. Despite compressions, Dean's pulse still hadn't settled down when the paramedics arrived. All Sam remembered afterward was the sirens and the beeping.
Carefully Sam drags him toward shore. A jolt or shock could be all it takes to disrupt his heart. A moment later, Sam grabs him under the arms and pulls him up the bank.
Apparently, straightening up is all it takes to wake up his lungs. Dean coughs, spits out a bit of water. His chest continues to move, if shallowly. Good enough for now, Sam decides.
Luckily, the laundry bag is in the trunk. Sam digs through it frantically, finds a flannel shirt and a blanket. He has no idea which of them the shirt originally belonged to, and he doesn't give a damn how bad it stinks from its last wearing.
He strips Dean of hat, coat and boots. The jeans are already beginning to freeze stiff, and Sam cuts them off impatiently. The skin beneath is blue-white, and just in time Sam remembers not to rub it dry. The shirt does a decent job of blotting up the loose water on his skin, and Sam rolls his brother onto the blanket and wraps him up.
Dean's heartbeat is steady, but still unnaturally slow. He isn't shivering, not much, and when Sam puts an ear to his chest, his breathing is wet. Sam lifts him into the back seat and frowns. All hypothermia aside, pond water deep in the lungs is a great recipe for infection. Dean will need antibiotics and steroids to hold off pneumonia, and maybe something to help clear the water out. And Dean's heart still isn't entirely out of danger.
Hospital. Definitely.
Sam slides into the driver's seat and wonders what that crackling is.
It's the ice on his own clothes breaking.