That's an interesting tale Bryan. I've also heard that in the Dardanelles fishing boats can lower a weight deep enough to catch the counter current and thus apparently go against the flow on the surface. Same sort of effect apparently.
You have been posting some very interesting illustrations, I think I shall have to print some of them off for future reference.
Counterflow is (as far as I know) only found in the straits of Gibraltar where the trawlers (except they aren't trawlers) can let the boat float out on the warm water and the cold water coming in keeps the nets out. BTW did you know that there is a huge ( 8 mile wide and 500ft tall cold waterfall at the Med. end of the Gib straits?....underwater of course, otherwise shipping would have a problem.
Whilst I am on this subject (?), I really should have given an example of "speed through the water" as opposed to "speed over the ground".
A lovely example is the St. Lawrence River in Canada. There is a section of the river where ships that do 11 knots or so have to be going "full ahead" to stay still against the outflowing river and tide. When the tide reverses these slow ships (over the ground) go like McLarens F1.
There is also an area up there where a waterfall flows both ways. I used to know how that was ....but dotage creeps in. Another anomaly re. the St Lawrence is that of the mirages. This sounds creepy but it is quite true...seen it myself. Trundling up towards Montreal (Benledi, 1959) 20 miles offshore the Pilot grabs me (cadet)(in the nicest possible way) and says " Watch this"....all of a sudden the shore 20 miles away comes into view, but upside down. In one of the houses a lady is waving. It is the pilots wife. She can also see him (upside down). True. Something called "ducting" I think. Same reason you can see the lighthouse on the Horn of Africa from nearly 1000 miles away if the conditions are right...and the lighthouse keeper hadn't been eaten by the locals. Also true. Many similar tales, but you are bored now.
However, the Dardonelles and (particularly) the Bosphorus are unique in that they are the largest donor of water to the Med. Water does not flow into the Black Sea..it flows out. Quickly. Another example (of us) doing revs for 20 knots on our way to Odessa but only doing 7 knots over the ground. Coming back home was a somewhat different story! I was the "driver" and believe me it was hairy, scooting past large mansions with maybe 50' to spare on a 660' long ship doing in excess of 30 knots. Loved it!! BY.