Together we can sort this!
I have recently found a pewter tankard in a skip (no surprise there then!)
It is engraved thus :-

                         PRESENTED TO
             LT. CMDR. SIR M. ROSE.K.S. O.C.O. S.S.
                      FROM CAPT.AND CREW
                         H.M.S. SOAK
                      "UP PERISCOPES"

There is no "S" class sub. called "soak" - not a surprise.
Lt cmdr Rose not listed anywhere in RN records or found by any search engine?
My mate "Salty Sea Dog" has never heard the term before.
So what is this all about them?
Look fwd. to solving this
Regards Skippy