Rather than being a full drinking game, "Waterfall" is usually a game played within other games such as Kings

Kings (drinking game)

Kings is a drinking game that uses playing cards. It is common among university students in Canada, South Africa, Chile, New Zealand, Australia, the United States, the United Kingdom, Ireland, Sweden, the Netherlands, Lebanon and Belgium. Players must drink and dispense drinks based on cards...

or Bergen's Baseball. The game is set up so that all players are arranged in a circle and begin to drink beer at the same time. Players can only put down their cup when the person before them in the line puts down theirs (usually the person who draws the Waterfall card is considered first in line). While possible with just a few people, the game gets especially exciting as the number of participants increases.