GALLEY (אֳנִי, H639, fleet). A long, low seagoing vessel, propelled by sails and oars, or by oars alone.
Hebrew is used collectively of “ships, fleet,” but אֳנִיָּה, H641, denotes “a unit of a fleet,” i.e. “a single ship.” It is the former that is employed in Isaiah 33:21 (“fleet with oars”). Obviously, the reference is to galleys propelled by oars and used primarily as warships. The passage teaches that the Lord is Jerusalem’s defense. She will be like a great city protected by rivercanals, into which no hostile ships (“galleys”) may venture. Thus, the galley of antiquity could be either a small or large vessel and was usually manned by oarsmen (“rowers,” Ezek 27:8). It is of interest to observe that the Heb. root under discussion is attested as a Canaanite gloss in the Amarna Letters: anaya (245:28).
International Standard Bible Encyclopedia (1915)
See SHIPS AND BOATS, II, 2, (2).