Liquid chalk. A liquid version of the traditional block chalk that has been used to improve grip in weightlifting, climbing, and other sports that require grip strength.
The name derives from the texture of actual shark skin. Shark skin will allow a hand to move freely in one direction while halting the hand if it were to move in the opposite direction. Liquid chalk or sharkchalk goes on smooth, then grips.
A game where one person attempts to bite the butt of someone while walking up the stairs behind them. Usually the biter yells out "booty shark!" right before they attack.