A Sterling engine requires a heat source to run. I also ask you how one could hide underwater recharging outposts and the subsequent electric bills, and how one could make a recharging "network" that covers the whole sea floor.
You seem to think that because you can imagine a way it can work (Sterling engines!!!) it is clearly done that way. You lack the evidence to prove that it is. Find me a Navy officer that says "yeah, they're really Sterling engines running off of the metabolic heat of squid" and I might start to believe you.
Also, unless you bring some evidence to bear and start being serious, this thread will go into the can.