阅读题请教

Thrust is used to propel the fish forward, and lateral force tends to make the fish's head deviate from the course in the same direction as the tail.

请问这里deviate from the course in the same direction as the tail. 怎么理解啊？

course: 前进的路线, deviate from: 偏离, lateral force:侧向力

deviate from the course in the same direction as the tail: (侧向力使)鱼的头和尾(向同一边/方向)偏离(鱼的)前进路线.