DSK wrote:
....
What "Ellen" was trying to say is that the boat could be making sternway
at approx the same rate as the current, leaving the boat effectively
dead in the water and the rudder would have no 'bite.'

Yes, I guess that's what she's thinking. But from the perspective of
the two sailors, the current doesn't exist. If there was a fixed
object, like a starting line, then this gets more interesting.