Does a sea zone have to be uncontested for a convoy disruption to work? Japan sub beside java (uk owned) uk rolls in a crusier to kill the sub, sub submerges. Does the sub still cause a convoy disruption?
A seazone does not need to be uncontested - the simple presence of an enemy ship disrupts the convoy, even if friendly ships are in the same seazone. If the allies has a ship in SZ6 at the mobilize units phase of Japan’s turn, Japan could not prevent the disruption in any way, even if they placed a far numerically superior force. If there’s an enemy ship, it disrupts - end of story.
“Submerging” has no impact on any game phase beyond the combat phase - it is ONLY an ability of the submarine to disengage from the battle and remain in the same seazone. The only time submarines can “submerge” is during combat and after combat is over, submarines are no longer considered submerged. It is simply a retreat mechanism, it does not exist in any manner outside of the conduct combat phase.