Ferrying is crossing a river, by propelling oneself (either swimming or in a boat) diagonally across and against the main current. In e.g. a canoe it's easy to do so without being pushed downstream at all, while when swimming you will lose some ground. The skill is knowing the best angle to take.
"ISTM" is "it seems to me", in any online discussion. b^)
"ISTM" is "it seems to me", in any online discussion. b^)