hǎi / shàng / de / tiān / qì / biàn / huà / mò / cè / chuán / yuán / bì / xū / suí / shí / zhù / yì / fēng / xiàng

海上的天气变化莫测，船员必须随时注意风向。

The weather at sea is unpredictable, so sailors must constantly watch the wind direction.