What is (a) The blade of an oar, or the thin part which enters the water. (b) The backward current or disturbed water caused by the action of oars, or of a steamer's screw or paddles, etc called?

wash — (Naut.) (a) The blade of an oar, or the thin part which enters the water. (b) The backward current or disturbed water caused by the action of oars, or of a steamer's screw or paddles, etc. (Webster's 1913.)

Sources