also: せんびん
noun
surface mail; sea mail
Refers to postal items sent by ship, as opposed to airmail. Common in contexts of international shipping.
この小包は船便で送ります。
I'll send this parcel by surface mail.
船便だと届くまでに一ヶ月かかります。
It takes a month to arrive by sea mail.
noun
ferry service; steamer service
Refers to a regular shipping or ferry line, often for passengers or cargo. Less common than the postal sense.
島への船便は一日に二便あります。
There are two ferry services a day to the island.