Feather One's Oar
To feather an oar
is to turn the blade parallel with the surface of the water as the
hands are moved forward for a fresh stroke. (The Greek pteron
means both “an oar” and “a feather;” and the verb pteroö,
“furnish with oars” or “with feathers.”) The oar throws off the water
in a feathery spray.
“He feathered his oars with such skill and dexterity.” Jolly Young Waterman.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894