Michael Hearn Anna Houpt wrote:

Just for the fun of it, Why does a racing scull go faster when the oars are
out of the water, and slower with the blasdes in the water? (no it is not
drag)... Mike

Because as the paddler slides toward the stern, the motion plus the
inertia of the oars drives the hull forward momentarily. It's really
somewhat illusory, as the rower is actually slowing down and the boat is
just moving relative to his/her body. It's more of a "windup" than
anything else.