The above may have been too convoluted. I rewrote it as follows:
Submarines are only good for cheap casualties (like infantry are) IF the “hit” inflicted in battle came from a naval unit OR if a destroyer is attacking. If a hit in battle came from a plane, the submarine can take the hit (be a casualty) ONLY IF the enemy is also attacking with a destroyer. DESTROYERS ALWAYS MAKE A SUB AVAILABLE AS A CASUALTY. Since destroyers force a sub to “be available to be hit”, destroyers can backfire on their “users” if the “user” is trying to cherry pick battleships. It’s counter-intuitive to think of a destroyer as a bad choice for attacking a zone with battleships, but it can be true IF enemy subs are present.
Because the game treats subs as always being under the water (under the water does not equal “submerged”. This faulty term, “submerged” will be discussed later) submarines are often VERY BAD at defending their own battleships. Because, if a zone contains subs and battleships AND the zone is attacked only from the air, the “hits” will ALWAYS go to the battle ships. Bye-bye battleships. This is commonsensical as bullets and bombs - once they hit water - do not damage a sub much, even if the sub is just 20 ft. under the water; the water “cushions” the blows. Furthermore, the term “submerge” is really a misnomer. A sub in this game is ALWAYS under water, or “submerged” in a sense. That’s why subs can pass through hostile sea zones (unless a destroyer is in it) and hostile naval units can pass through subs. The term “submerge” should be replaced with “dive VERY deep so it’s useless for battle and cannot be hit”. In the game, when the sub is “submerged” it is essentially VERY DEEP in the water as just stated. “Submerged” is misleading because it implies that when the sub is NOT submerged it is sitting at the surface of the water where the guys are drinking beer, enjoying the view, and getting a tan. Subs are ALMOST NEVER in this sunbathing position; if they were, how could they travel through hostile zones?
FURTHERMORE, the rules introduce another VERY interesting concept. They actually say that a sub can be held hostage in a zone, unable to go anywhere unless 1) the enemy destroyer above it leaves or 2) the sub fights its way out. In other words, a sub, when under an enemy destroyer, must either fight or “be frozen”. So it’s kinda trapped! Just move your destroyer to the same zone as a sub and then choose not to fight it; then the sub will be frozen until you move! The sub won’t attack you on the sub’s “turn” (even though the option is there) if the firepower of your fleet above it is too powerful! This “freezing of the sub” occurs because the rules say “If a submarine enters a sea zone containing an enemy destroyer, it MUST end its movement there.” So my question here is as follows: If a sub decides to fight it’s way out, and after one round of combat an enemy destroyer is still above it, can the sub just “chill out” and “just be frozen under the water” again AFTER the enemy retaliates for that round? OR does the sub have to fight to the death?
So, you may ask, "how can a destroyer just peacefully sit in the same space as an enemy sub? It’ because the rules say: “Subs CANNOT stop enemy ships from moving above them in the water. Sea units ending their combat movement in a sea zone containing ONLY ENEMY SUBMARINES may choose to attack them OR NOT. Sea units can also end their noncombat movement in a sea zone containing ONLY ENEMY SUBMARINES.” But we all must remember, if we choose to sit above a sub in it’s same zone, that sub can attack us the next turn. As we said in the previous paragraph, a destroyer would keep the sub(s) frozen until the destroyer dies or moves. BUT, if NO DESTROYER is present, can the sub attack the fleet above for just one round, and then move two spaces away during non-combat movement IF the counter fire didn’t kill the sub? If a destroyer IS present above and the sub DOES kill it, can the sub move two spaces away during non-combat movement?