Hi Richard, I have worked a little with ROV systems specifically for supporting sub rescue.
The short answer is that the ROV supports the guys in the sub. There is absolutely no way the ROV would ever be allowed to intervene in the submarine without the guys inside agreeing. Only if they are certain that the sub is full of non-survivors would the ROV intervene directly.
DISSUBS communicate by underwater acoustic telephone. NATO standard kit. If the telephone is not working then there is an international set of hull tapping codes. (ROV needs a hydrophone).
All subs in recent decades have "ventilation" points. ROVs connect special hoses from the surface so they can recirculate air. Air sampling is done on the surface. There is a NATO public standard on this.
The long answer is quite long, I have some material that is more than should go on a forum post. An old, but still excellent, book on sub rescues is "Few Survived" by Edwyn Gray – get it second hand on Ebay or Amazon.
I don’t want to post my email address on this public forum – but I think there is a way to send messages to a member. If you find the way, send me a contact and I can send you some detail material on this.
(ROV intervention on military subs is not a big group of people).
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