The only reason in 1942 why you can’t submerge a submarine is when the other side has at least 1 destroyer in the battle. Destroyers cause the submarines of the other side to lose both their submerge ability and the surprise strike ability. Such submarines fire with their fellow attackers and defenders as normal warships do.
An example: Germany has 2 submarines and 1 bomber attacking a UK fleet with 1 cruiser, 1 destroyer, 1 submarine, and 3 transports. The German subs lose their surprise strike because of the UK destroyer, the UK sub retains its surprise strike because the Germans have no destroyer in this fight.
Round 1: UK sub makes surprise strike roll, missing. Germany rolls attack for 2 subs and 1 bomber, gets 1 hit - UK loses its destroyer (not the choice I would have made, but I’m making up an example of what would happen if). UK rolls defense for 1 cruiser and 1 destroyer (the submarine already fired), gets 1 hit. Germany takes 1 sub for the hit.
Round 2: Both the remaining German sub and the remaining UK sub get their surprise strike - Germany hits, UK misses. UK now takes the sub for a hit. Germany now rolls attack on the bomber, getting another hit. UK has to take the cruiser for the hit. UK rolls defense on the Cruiser, gets a hit. Germany chooses to lose their remaining submarine.
Round 3: one German bomber and 3 defenseless transports - auto-kill of the transports and any cargo by the bomber. End of combat.
At any point in this example, any of the submarines that were able to roll for surprise strike at that time could have submerged instead of fighting. That would have been only the UK sub in round 1, because the UK destroyer removed the German subs’ surprise strike and submerge abilities. After the destroyer is sunk in round 1, both the UK sub and the German subs could have submerged at the start of round 2.
At the start of round 3, the remaining German sub could have submerged, but that player choose to use surprise strike instead.
Clear? Or clear as mud?
Edit: Lost track of my subs…