Diver0001:I have a sign for that situation.
I use upturned palms to indicate "I don't get it". Then I point at my temple to say "remember this" and then make a little talking motion by opening and closing my hand in front of my reg to say "tell me later". All together you get
"HUH?", "remember", "tell me later".
If he gives me "OK" then we're done. If not then he's probably already writing it down...
R..
My buddy and I got seperated from our "guide". We comenced to have a whole long conversation about should we abort the dive or go on and wich way we should go. It was quite comical now that I look back on it. But I would rather do it that way then have voice communication. I can see how it would be very useful for rescue operations and such tho.