Any military nerds here?

 

http://upload.wikimedia.org/wikipedia/en/3/3e/OP_KILO.JPG

 

This is a Russian built (Iranian service) Kilo Class diesel-electric attack submarine. I'm about to build a model of one which is why I'm researching it. What I'm wondering about is what those little white painted rings on the deck are. Do they serve some functional purpose? The Kilo Class has two, some Soviet submarines seem only to have one and American submarines don't have any at all. Quite the quandry.

perhaps they mark out escape hatches?

Yeah, probably docking rings. They'd be painted to make them more visible. American subs may not have the painted rings, but they do have escape hatches.