What’s a Screamer?

What’s a Screamer?
At Sea on patrol in the med can be very boring. And in fact it was on several patrols I made from Rota Spain back in the early '70's. 
The med being relatively small with considerable surface traffic, not to mention submarine traffic, is not the most forgiving place to make a mistake. 
Dozens of surface contacts are encountered and tracked everyday. By the end of patrol many hundreds or even thousands of surface contacts have been logged tracked identified and maybe even had the opportunity to be visually identified. 
We had been at sea for some six weeks and patrol routine was the only comfort in the minds of most of the crew. 
It was after the evening meal and the movie was in the middle of the second reel in the crews mess. 
The crew making its usual comments and laughing during the movie. There was a lull in the action and one of the Nukes asked "what is that noise?" Most of us couldn't hear it. A few moments pass and again he asks "don't you hear that?" The projector was stopped and we all listened... above the noise of the ventilation system and the fan room outside the mess... then there it was... a steady rhythmic thump thump thump."Oh SHIT!" He yelled. Everyone ran to their battle stations as fast as we could... seconds later the collision alarm went off. The entire boat shook violently, we never actually collided but the vibrations from the screw were very strong, the noise was surprising and then... nothing...
As we secured from battle stations we all looked at each other and several of us went up to sonar to comfort the deaf sonar technician that almost killed the entire crew single handedly. 
He was in the process of being relieved under orders of the OOD. 
It wasn't long and we were back into the routine of patrol.
Finally, the only watch everyone looks forward to at sea, the maneuvering watch, was set. 
In Rota Spain, the maneuvering watch is very short. As we all ran topside to get her rigged someone noticed a peculiar pattern of markings on the missile deck running at an acute angle to the fore-aft axis. About three inches wide at its widest and about three feet long with a spacing between them of several inches. The paint had been removed right down to the metal! 
The only thing we could figure was... you guessed it, that screamer was A LOT closer than we had originally thought!!
Despite the time crunch three of us took a moment and thanked God for seeing his way clear to look out for a bunch of sailors in a hole in the ocean.