Thank you guys. That was very helpful!

I came across the following scenario:

The attacker wants to conduct an amphibious assault on a land zone containing an airbase. He attacks the sea zone with planes only and wants to attack the land zone later using loaded transports and planes only. The defender has one destroyer and one submarine in the contested sea zone and scrambles one fighter.

Question 1) Does the submarine participate to the sea battle (even though it can neither attack nor get attacked)?
Question 2) Is the answer to Q1 still “yes” if no scrambling takes places (only destroyer and submarine defend)?

Now suppose that all defending units (the destroyer and the fighter) have been destroyed by the attacking planes during the sea battle, only the submarine remains in the sea zone (because it could not get hit by the attacking planes). The defending submarine was NOT submerged by the defending player using the “Submersible” rule form the rulebook (I think it could not anyway since there was no attacking warship in the sea zone, but just to be safe …).

Question 3) Does the surviving submarine block the transports after the sea battle (that means the attacker has to abort the amphibious assault)?
Question 4) Is there any change of the situation if the attacker brings additional cruiser and/or battleships for bombardement?

Many thanks in advance!

Daniel