Draco had been falling so long he started to get bored of the images of his father giving him his first broomstick when he was three; having to hang out with crabbe and goyle all summer because he had no one else to hang out with; the first time on the Hogwarts Express when Weasley laughed at his name and Potter refused his friendship; dancing with Parkinson at the Yule Ball; finding out his father was in Azkaban – THUD!
"Aaahh!" cried Draco, the wand falling out of his clenched teeth. He'd landed in something crusted and slimy which had, nevertheless, padded his landing. He was surprised to find that he still had the sapling clasping in one hand, and the earplug in the other. This he hastily jammed into his other ear, and was relieved to find it stayed.
It was completely silent. So silent that he didn't hear the rush of little flapping wings and squeaks, and the air was suddenly thick with bats, catching on the fur of his cloak, slapping him in the face and pulling at his white-blond hair. Draco squeezed his eyes shut and brandished the sapling as wildly about his head as he could. Groping around in the slime he managed to find his wand, and the teeth marks on it, and yelled, "Reducto!"
There was a kind sonic of boom (which Draco couldn't hear of course) as the bats were propelled away from Draco. He ran for it, his bags over his shoulder, and kept running until he tripped over a stalagmite and barely saved himself from falling flat on his face. Panting he looked up at the cave around him. It seemed as if the moon was somehow shining through holes in the mountain, illuminating the enormous cavern. Stalagmites and stalactites reached towards each other, the walls glittered and were reflected in the pools of water on the floor, which were deep and seemed to be interconnected… it was very peaceful.
Draco noticed that his mouth was hanging open, and quickly made to shut it. His mother had always reminded him how unattractive it was. Yet just looking around the room he couldn't help but feel awed. After a while the bat guano was starting to sink into his good fur-lined cloak. He wondered if he should wash it, but having never done it manually himself –thanks to servants and house elves- he wasn't sure if he should put the fur in water. In the end he figured that whatever animal the fur had come from, probably was H2O tolerant; and so he headed to the nearest pool and started soaking the guano while using his fingers to scrape it off. After about five minutes it was pretty much clean and he was just admiring his work when a snake-like head lunged out of the water and took a bite out of it.
"HEY!" Draco yelled at it crossly, then realized, as it reared up, that the creature's head was attached to an extremely long, flexible neck connected to a huge body, most of which was submerged in the water.
"Aaaaaggghhhh!" screamed Draco, and, never having been the one for heroics, he turned and ran right into a patch of bat guano. He slipped and slid right down a sort of water slide.
Draco started to think that he might be in a little bit of trouble. For about ten minutes his hips kept thudding painfully against the sides of the 'slide' and he was soaked through. He must be far beneath the mountains now. Suddenly he shot out of the slide, momentarily soaring through empty space, then he was underwater. Icy cold water into which he was sinking. His bags ballooned. For a split second he wondered if it was now raining in the zoo aviary, then he remembered he had to breathe and started kicking viciously upward. He emerged and…