Rather than describe the scene, I'll show it to you:
This is Mirror Lake on a normal day. Scenic and calm.
This is Mirror Lake on the night of the jump. Crazy, loud, and fun.
And here's some video, set to a crappy rap mashup, that gives you a sense of the scene.
It's yet another example of activities that are considered normal in college, yet clear examples of insanity out in the real world. I'm looking forward to it.