Upon further review, the officials have decided that Fluckey's raid, while conducted in water 60' or less in depth, in uncharted waters with rocks all poised to rip the bottom out of the sub, and with three frigates guarding several (Fluckey says 24) anchored ships, and with extensive fleets of junks and sampans making the run quite exciting, this in no way conforms to the Mediterranean definition of a harbor. Granted, Fluckey had to run six or seven miles just to get to the 10 fathom curve, then an additional ten to get to the 20 fathom curve where he could dive, and he was pursued by at least one of the frigates during that egress, this is quite a different position than that found in the Mediterranean or Atlantic theater.
I don't know which is really more difficult, this one with miles of shallow uncharted, rock infested water, or a precisely known but scientifically defended harbor. Obviously both were penetrated successfully by submarines, proving that the submarine was equal to whatever challenges existed in either theater of war.
Fluckey's account in "Thunder Below" in the chapter on Barb's 11th war patrol (!) is one of the most exiting accounts by either Americans or Germans in WWII, and surely comes close to Prein's conquest of Scapa Flow, minus the glamor targets and guns from capital ships waiting to vaporize the little U-Boat. Fluckey's battle was much more evenly matched, in spite of his handicap from all the shallow water and sampans. It is also safe to say that the moral effect of Prein's attack on the British was far in excess of the effect of Fluckey's attack on the Japanese.