Submarine question

Do you get to chose at any point when they’re surfaced, and submurged?

Submerging works like this:

After a round of combat (both sides roll dice), the attacker chooses whether to retreat or to press the attack. If you choose to retreat, the submarines can submerge; submerging is simply their special way of retreating. They can still retreat like normal by moving to an adjacent sea zone like other naval units, but submerging allows them to sit in that sea zone immune until next turn. If the attacker chooses to press the attack, then defending subs may submerge. Any living destroyers will cancel enemy subs ability to submerge.

Basically you can only submerge after a round of combat. Submerged submarines surface at the end of the current player’s turn, regardless of who controls the submerged subs.

For example, the UK attacks 2 German subs with 1 fighter. He scores a hit (the subs can’t fire back at air units). But at this point the German player decides to submerge his remaining sub, thereby escaping certain doom from the fighter. The sub surfaces at the end of the UK’s turn.

Or another example, the US attacks with 3 subs against one Japanese battleship. The subs score one hit in the first round, and the Japanese scores one hit too. The US can at this point either retreat the subs normally or submerge them .

The biggest thing is that submerging occurs after BOTH sides have fired.

You can;t charge in with subs, fire sneak attacks, and then submerge to avoid a counter-attack by any surviving defenders.  The defenders get to fire back, then before anyone fires again, both attacking and defending subs can choose to submerge (leaving the battle)