@mateooo:
personally, it seems to me that they should only be able to submerge… retreating would give them way to much ability to get around… but whats the official rule?
Yes. The retreating to an adjacent sz could be quite deadly.
For example in Classic, had you gotten the rolls you did at Pearl, after rd 1 of battle I would have retreated my sub from the battle.
Then you can use it a counter to Pearl or even harass Japan trannies that are unprotected in Jap sz or nearby.
I guess DD’s help stop some of that and the rule change makes sure subs at least can’t gain an extra move.