thanks the FAQ is a big help

Hello, I am A noob to Axis and Allies, as well as this forum and have a question.
I am playing the revised addition 2004, and cannot locate in the rule book how air units attack subs.
Can air units attack lone subs or groups of subs in sea zones?
After the initial attack can the sub submerge?
or is the sub allowed to submerge before combat to avoid air attack?
My biggest question is where does the rule book explain this combat scenario?
Thanks