also: そとうみ
noun
Refers to the sea outside a bay, harbor, or inland sea; the open ocean as opposed to coastal or enclosed waters.
台風が近づくと、外海は大荒れになる。
When a typhoon approaches, the open sea gets very rough.
この港から外海に出るには、狭い水道を通らなければならない。
To reach the open sea from this port, you must pass through a narrow channel.