I concur with P@nther. However, I have the Revised manual in front of me and it states on page 32:
Treat Hostile Sea Zones as Friendly: A submarine can move through a sea zone that contains enemy units. However, if it ends its combat move in a hostile sea zone, combat will occur. A submarine cannot end a noncombat move in a hostile sea zone. The presence of an enemy destroyer in the same sea zone forces a submarine to stop moving."
But the official Errata/FAQ for Revised states:
"Submarines
Subs have always been confusing. Can you summarize the changes?
Here’s what you need to remember about subs.
1. Every sub, regardless of whether it’s on the attacking or defending side, fires in the Opening Fire step of combat. That’s the only time a sub ever fires.
2. Losses caused by attacking or defending subs are removed at the end of the Opening Fire step, before normal attack and defense rolls, unless the enemy has a destroyer present.
If the enemy (attacker or defender) has a destroyer, then hits caused by your subs aren’t removed until the Remove Casualties step (step 6) of combat.
3. In other words, subs work exactly the same for the attacker and the defender. Nothing, not even a destroyer, ever stops a sub from rolling its die (attack or defense) in the opening fire step. What a destroyer does do is let you keep your units that were sunk by enemy subs on the battle board until step 6, allowing them to fire back before going to the scrap heap.
My sub attacks an enemy destroyer and hits it in the opening fire step. Does the destroyer get to shoot back?
Yes.
My sub attacks an enemy destroyer and aircraft carrier and scores a hit in the opening fire step. What happens?
One of the two enemy ships is designated as taking the hit (moved to the casualty area of the battle board) but neither is removed from the battle board yet. Both get to shoot back. Let’s say they both miss (rotten luck). In step 6, the casualty is removed. If the destroyer is removed, then the sub has a chance to hit and sink the aircraft carrier in the next round before the carrier can return fire. If the carrier is removed, the sub may hit the destroyer in the next opening fire step but the destroyer is guaranteed a return shot no matter what, because it’s a destroyer.
Assume that my attacking submarine submerges and then the surface ships of my attacking fleet are sunk. What happens next?
The submarine surfaces at the end of the non-combat movement phase, regardless of what’s in the sea zone. The opponent can shoot at it again during his next combat phase, or move away from it during the combat move. (Nothing prevents the beginning of movement during the combat move, not even the presence of an enemy unit in your units’ space.)
Can submarines attack or defend against fighters? What happens if a lone fighter attacks a sea zone that has four enemy subs in it? Can the subs defend themselves and destroy the fighter, or are the subs just sitting ducks until they submerge?
Submarines can only hit sea units (p. 15). They must suffer a round of fire from the fighter before they can submerge.
My sub attacks an enemy battleship. Can I sink it with my opening fire if I roll a 1 or 2, or does it still take two hits to sink a battleship?
It always takes two hits to sink a battleship. Two subs attacking a battleship could sink it in opening fire if both hit. If only one sub attacks, the battleship is guaranteed to get a return shot no matter what because a single sub can’t cause more than one hit per round. If the battleship was hit in the first round and its return shot missed, then the sub could sink it by hitting it again on the second round. The battleship would not get an attack on that second round because it sinks right after the sub’s attack.
An enemy sub attacks my sub. When can I submerge?
In the Press Attack or Retreat step, same as always.
An enemy sub attacks my sub. If I shoot back during the opening fire step, can I still submerge in the press attack or retreat step?
Yes.
Submarines are part of a large naval engagement. Do they get to fire during the opening fire step of every round, or only the first round?
Every round.
On the UK player’s first turn, he attacks my German sub with a fighter. He rolls and misses. My sub submerges. When does it resurface?
At the end of the UK player’s non-combat movement."
And that is all I know about the Submarine rules for A&A Revised.