Water trough

From USAFA Folklore

The water trough is a trick played on a cadet sitting towards the end of a table in Mitches (normally an upperclassman). All the other cadets on the same side of the table grab the bottom of the table cloth and lift it to create a sloping trough. A whole pitcher of water is poured into the trough at one end which is then deposited into the unsuspecting cadet's lap.