Something called "hallway swimming" is taking off on YouTube. a kid in Canada posted a video of himself doing it, and now a bunch of other people have too.
Basically, you find a hallway with a freshly buffed floor, and walls that aren't too far apart. Then
you lie down, and pretend to 'swim' back and forth across the hall by kicking off the walls, the way you would if you were doing laps in a pool.