People participate in the National Flipper Race at the Dam Square in Amsterdam. Photo by Ade Johnson.
Flip out 失控暴怒
Leonardo da Vinci was one of the earliest inventors to work on the concept of an artificial flipper to help swimmers. The American inventor Benjamin Franklin also made an early design from wood.
達芬奇是研究如何用人工腳蹼（蛙腳）來提高游泳速度這一概念的最早的發明者之一。美國的發明家弗蘭克林也曾發明過木質的蛙腳。
英語短語 to flip out 意思是由於震驚而失控暴怒。
When Kate heard that she hadn't got a place at her first choice of university she really flipped out and started shouting and screaming.
The flight was cancelled and lots of passengers started flipping out at the airline staff.
The flip side 是另一個意思，表示反面，特別指物體或論點的負面，不利面。
The Olympics is a great event; on the flip side it's very expensive to host.