Thanks, mates. Your tips are all very helpful.
I am finally learning to use the high-frequency active sonar now. I've gotten in some practice by tackling a couple missions under the ice where it's really essential, as Stanny said.
(I felt totally like I was in "Ice Station Zebra!" 
)
Now that I've had success using it there, I have a bit more confidence to go back and try that Strait of Hormuz mission again, and see if I can detect any mines. I had completed that mission once, but it was truly nothing but dumb luck that I didn't tag another mine, since I didn't know how to safely look for them.
That's really interersting about the radio message you got, Sonar732 ... I never think to check for radio intel during my missions. Something for me to keep in mind, thanks.
I'm still a pollywog, but I'm gettin' there ... I hopefully won't be one forever.
P.S. M.L., lol@"Minesweeper: The Movie!"