Whamwhamwhamwhamwhamwham........WHAM!
Keith Nicholas, 2nd year extraordinaire, hit the bottom of the stairs with a nearly bone shattering thud after leaping into the air halfway down. Despite the cold outside (which was leaking through the magical defenses, making Hogwarts itself rather chilly) he had already stripped his shirt and wore only a baggy pair of shorts. He was barefoot, and nearly killed a teacher as he burst through the large doors to the grounds.
The towers had attracted them from the common room - Keith's room in particular had an excellent view of the lake - and he had immediately been intrigued. Then people had started jumping off the towers, and Keith's mind was officially blown.
He tore over the ground to the lake, (he figured to himself that he must've set some kind of record with that sprint) and hit the water full force with an ear splitting cry of "WHOO-HOO!"
Now, Keith had never been the best swimmer. But what he lacked in technique he made up for in sheer enthusiasm, reaching the tower and immediately beginning the climb. Whoever had constructed the towers had layered the things in protective enchantments, making a normally impossible climb fairly simple. Keith's wet hands stuck to the rock in mind bending ways, giving him a very spider-man-esque feel as he scaled the tower until he reached the top.
He could see for miles (or at least, he imagined he could) Amazingly, he wasn't cold, the lake must've been enchanted to keep at a warmer temperature than was normal for this time of year. Keith stuck both fists in the air in an expression of victory, grabbing a free rope on the opposite side of tower as Brienne had jumped off. He wrapped it around his waist and leaped.
The wind rushed through his hair, making his eyes sting - Keith would've screamed from the awesomeness of it all if there was any air in his lungs. Instead he hit the water (something that from this height really should've killed him) and felt the rope tighten around him as it reached it's limit.
Keith opened his eyes underwater, and for a brief moment was treated to a picture of a school of fish staring at him in shock. Then the rope contracted, and Keith was pulled out of the water, flying into the air like some kind of rocket. He whooped in victory before hitting the water again, this time staying much closer to the surface as his momentum disappeared. He surfaced, spitting water out of his mouth and laughing. "Again! Again!"