Caught the tail end of a German programme the other day about submarines and the Bundesmarines latest toys. The bit I found interesting was the mention of a wire guided torpedo with a range of 20 kms. That invites the question, what is the maximum range at periscope depth at which a reliable visident can be made on a potential target (sea conditions permitting) or could a target be attacked using sonar information only? Another point of interest was the German Navy's practice of bouncing unsuspecting surface vessels including their own Navy. Does the RN do that as well. No intention to compromise Opsec here.