A route by sea; a sea lane. Also used adverbially to mean 'by sea' or 'via maritime transport'.
貨物は海路で輸送されることが多く、コストが安い場合がある。
Goods are often transported by sea, which can be less expensive.
彼らは海路をたどって島へ渡った。
They traveled to the island by sea route.
冬季は天候が荒れるため、海路しか選べない地域では影響が大きい。
In winter storms, areas that can only be reached by sea are greatly affected.