All steam so far. Early in the war, the combination of high torpedo speed and shots from 800m or less seems to have been pretty effective.
In either case, I haven't seen much indication that early war merchants pay much attention to torpedo wakes. On a number of ocassions I've seen torpedos pass under merchants or impact but not go off with little indication that the merchants either saw or cared - though seas were calm enough I can't imagine how they couldn't have seen. Example: At one point, I hit a C2 at too sharp an angle, resulting in two duds. I was actually able to surface for an end-around and attack again, and the C2 hadn't changed course or speed. :hmm: These early war mechant watchment need to get their act together. Or maybe lay off the rum ration.