The sea was rough and half the passengers were seasick.

海面波涛汹涌,半数旅客晕船。

上句中的rough不是指粗糙的，而是形容海面波涛汹涌的。

seasick只晕船的; carsick指晕车的； airsick指晕机的。

It was a bumpy ride, many passengers got carsick.

那车程很颠簸，许多乘客都晕车了。