AN: I know nothing about caves or diving beyond what I've read on the internet or seen in movies, so please forgive any inaccuracies in the next few chapters.

I've used the Spring Cave of Colorado as an inspiration for the one in the Supernatural universe, but while they may share features, they are not the same. This is especially true in terms of scale.

Kensi followed Sam's tall form up the rocky trail, enjoying the pretty morning in the mountains. The air was fresh and clean, the birds were singing, and it seemed a shame that they would soon forsake the bright sunny day for a cold, dark cave. She noticed that Deeks wasn't voicing his usual complaints, and wondered if he was starting to appreciate woodland environs. What she didn't realize was that he was busy, trying not to be obvious about it, but keeping himself physically interposed between her and Dean.

Bringing up the rear, Sam and Callen watched the jockeying for position going on behind the oblivious Kensi and fought not to laugh aloud.

As predicted, the lock on the cave gate proved to be no barrier to their skills. Kensi wrinkled her nose at the unpleasant smell of bat guano, but knew that it would fade out before long. The bats, unlike them, were smart enough not to penetrate very deeply into the caverns.

They stopped a short way into the cave, where it was still light enough to see, and unloaded the gear they'd need immediately from the backpacks. They put on the warm, water-repellent, reflective coveralls known as cave suits, and donned the helmets.

Callen looked into the dark maw ahead, where monsters potentially lay in wait. 'Creepy,' he commented.

Sam shrugged, 'At least it's not clowns.'

Sam Winchester looked up from where he knelt by his backpack, and smiled. 'I know, right?'

The first part of the tunnels showed evidence of a great deal of vandalism. Dean pointed out that, among the names, dates, and other graffiti humans had scrawled on the walls, were a number of esoteric symbols.

'Those are Enochian,' he said, shining his light at some written in white chalk. 'They keep out the angels.' He swung the light to some red ones, 'And those are anti-demon. I don't know what they've got rigged to detect humans, but we're not setting off any audible alarms, anyway.'

That didn't stop anyone from being nervous.

They began to descend quite soon. The first drop was easy, as someone had installed a wide metal ladder. It showed signs of wear, but was still sturdy enough. However, that was the last artificial assistance in evidence. This was no tame, tourist cave.

As the natural light faded away behind them, they learned the true meaning of darkness. They could see nothing outside the circle of light cast by a headlamp or hand light. A great deal of attention was called for, to watch both one's head and one's feet at the same time. There were no flat surfaces, and the height of the ceiling varied from step to step. It was, in fact, rather cramped for large adults carrying a good deal of gear.

Before long, the cave became their world. It crowded close around them, cool and damp. The silence pressed in on them as well, the incredible quiet disconcerting to people accustomed to the myriad noises of the surface world. All they could hear was their breathing, their feet upon the rocks, the shift and rustle of clothing, and the distant sound of running water, from somewhere up ahead.

Deeks, whose surfer's soul rejoiced in the bright, wide-open expanses of sea and sky, found the close press of darkness and rock very confining. In many places, there was no room to maneuver, should it come to a fight. And whoever had the point position, or brought up the rear, was particularly vulnerable. Callen had insisted on going first, of course, and Sam was close behind him. He and Kensi were next, followed by Dean and Sam.

He certainly hoped they could get in and out without incident. The monsters definitely had the advantage, in this environment. It wouldn't be a good idea to fire a gun down here; besides the dangers of ricochets, you'd deafen everyone. And the best weapon against a Leviathan, a sword or machete, could not be effectively swung unless you were in one of the more open spaces. Footing was treacherous, as well.

And then there was the issue of light; they were completely vulnerable without it. If the creatures managed to destroy their light sources, they'd be able to pick off the team at their leisure. With the amount of damage they could take, the monsters could launch attack after attack, in ways that would be suicidal for anyone else.

But, they were committed to this course, so they pressed on despite the dangers. Kensi thought she might actually have enjoyed the experience, under other circumstances. It was very different than anything she'd tried before, and she was always up for new challenges. Being the smallest person there, she was also having the easiest time negotiating the tight spots, especially where they had to remove their gear in order to squeeze through. She was not happy about how vulnerable they were during such transitions, though.

At first, they travelled in silence, alert for any sign of guardians. After a couple of incident-free hours though, and with the increasingly loud rush of water drowning out other noises, they began to relax their vigilance. They were all also feeling a need to connect with other human beings, in this alien environment. After a brief stop for water and a couple of handfuls of trail mix, they continued on, but now spoke to one another as they went.

Deeks, eyes on his feet as he navigated a narrow passage, nearly walked face-first into rock as he rounded a corner. 'Thanks for the warning, partner,' he said to Kensi, who was ahead of him.

'Don't be a baby, Deeks,' her voice floated back. 'Just watch where you're going.'

Well, he could be courteous. He called out to Dean and Sam, behind him, 'Yo, tall and taller! There's a low point coming up, just past the curve. Watch yourself.'

'Thanks, man,' Sam replied. He was not happy; his back was already aching from stooping over so much of the time. He couldn't wait to get out of there, back to the surface where his large body was an advantage. This caving stuff was not for him.

Both Sam and Dean were very determinedly not thinking about their time in a different pit.

'So,' Deeks asked Sam as they passed through a larger room, 'if gods and such are real here, does that mean The Avengers are real too?'

The geography of the room had allowed Sam get ahead of Deeks. As he entered a narrower passage, Sam looked back and replied, 'Well, we haven't seen any, but I did get to use Thor's hammer once.'

'What? You... What?' Deeks hurried to catch up, determined to get the rest of that story.

They came to a fairly steep descent, almost vertical in places, and found that someone had left a rope behind. There was no telling how long ago though, or how reliable it might be. Still, it was more of an aide than a safety measure; the slope was navigable, given sufficient care.

Deeks was the first to try it, and he made it most of the way before his foot slipped on a loose rock. He slithered and slid briefly, then jumped away, trying for a relatively flat spot on the cave floor. He landed off-balance, but managed to recover, and straightened up with a flourish, pretending to 'stick' the landing.

Kensi, halfway down, had frozen in place when he'd lost control. He looked up at her, and said reassuringly, 'Don't worry. If you fall, I'll be right here to catch you.'

Sam, amused, called down from the top, 'You gonna catch me too, Deeks?'

Remembering what Crowley had called them, as well as an epic battle of rock-paper-scissors he'd won against Sun-Tzu-Sam, he replied, 'Nuh-uh. Moose squashes Squirrel. You're on your own, big guy.'