"Wildthing" is flying a hull downwind. It is an essential racing technique for modern cats- A class, F18, F16 etc.

Beginning at around 6knots of wind, bringing the weather hull out of the water when sailing downwind, results in an amazing increase in boat speed.

Typically, start out well forward, almost hugging the mast. As the wind increases, move back; as the wind continues to build, move to the high side.