:-) To assist you in injuring deceased equines:
http://www.wizards.com/default.asp?x=ah/faqs/axiseurope
When attacked, can submarines submerge immediately or do they have to survive one round of fire from attackers?
They have to withstand at least one round of fire. Otherwise they would be practically indestructable.
Hope that helps. :-) If the official FAQ doesn’t do it I don’t know what will.