It means the ship lost its direction

it means the ship fail or break down, as from being operated under extreme or improper conditions: whileof moving in a path from point to point. cowboy...

If you are on course, then you are going in the right direction. If you are off course (迷航), then you are going in the wrong direction. Sometimes the wind blows a ship off course, especially in a storm.

It means due to being blown about by the fierce winds, the ship lost its way and strayed from its original route.