Wiktionary
n. (context nautical English) A body of ocean water such as a channel.
Usage examples of "narrow sea".
But 'sheltered' did not mean much, where the Minches were concerned: this stretch of narrow sea between Stornaway and the Scottish coast was one of the wildest anywhere round Britain, an uneasy area with swirling currents, violent overfalls, and, at the northern end, the ceaseless swell of the Atlantic coiling in to set up a wicked cross-sea at any state of the tide.
Turk, seized, pillaged, and abandoned, each in turn, this stronghold overlooking the narrow sea.
Close packed the barges undoubtedly were but, although it would call for the most intricate manoeuvring, each barge had, in fact, access to a narrow sea lane, which might intersect with two or three progressively larger lanes before reaching the open water beyond.
I saw the narrow sea and, away to the east, the mainland of Britain.