They swim using a small fin on their back.

它们用背上的小鳍游动.

互联网

This fin reduces turbulence and hence improves the airflow passing close to the front wheels.

这片小鳍可以减少乱流,藉此改善通过前轮附近的气流.

互联网

Next, cut the pin at the small fin off.

跟著, 把小鳍下的胶柱剪掉.

互联网