Intrigued on if the Improved Los Angeles-class (from USS San Juan) has a ducted screw and it qualifies them for the "Does not cavitate" flag. I don't remember any photo of any Los Angeles with a ducted screw, but ...

 

Analysing navysource.org photos (I saw all the boats photos today!), some curious results here:

 

USS Jacksonville (SSN-699, Flight I) launching ceremony, unshrouded screw probably covered with tarpaulin:

http://navsource.org/archives/08/700/0869914.jpg

 

USS Buffalo (SSN-715,Flight I), clearly unshrouded screw (this was a very difficult one to detect in the thumbnails!):

http://www.navsource.org/archives/08/0871520.jpg

 

USS Oklahoma City (SSN-753, Providence VLS sub-class), probably unshrouded screw:

http://navsource.org/archives/08/701/0872331.jpg

 

USS Greeneville (SSN-772, San Juan I688 sub-class) in dry dock, showing a first glimpse of "the thing" covered by tarpaulin (whithout the next model photos, impossible to determine clearly his shape). But not evidence of a true ducted pump-jet: http://www.navsource.org/archives/08/0877226.jpg

 

Model of USS Greeneville (SSN-772, San Juan I688 sub-class), showing clearly "the thing", apparently a seven blade screw, entoured by a narrow annular circle welded to the blade tips. But not evidence of a true ducted pump-jet: http://navsource.org/archives/08/pdf/0877242.pdf

 

USS Cheyenne (SSN-773, San Juan I688 sub-class), annular circled screw covered by tarpaulin. But not evidence of a true ducted pump-jet: http://www.navsource.org/archives/08/0877329.jpg

 

 

As sideshow, an interesting photo of the JFK CVBG in the USS Albuquerque (SSN-706) section:

http://www.navsource.org/archives/08/0866913.jpg

 

Cracked sonar dome of USS Groton (SSN-694), caused by a air bubble not evacuated previously to going deep: http://www.navsource.org/archives/08/0869411.jpg

 

Launching commemorative booklet of Glenard P. Liscomb (SSN-685, forerunner of Los Angeles-class), with a comparative of US and Soviet naval forces!: http://navsource.org/archives/08/pdf/0868509.pdf

 

Curious and detailed model of USS Tullibee (SSN-597, a small, silent and slow hunter-killer submarine)(five blades screw?): http://www.navsource.org/archives/08/0859704.jpg

I remember this, the new Russian Yasen-class SSN has clearly an unshrouded screw and probably cavitates:

http://commons.wikimedia.org/wiki/File:%D0%A1%D0%B5%D0%B2%D0%B5%D1%80%D0%BE%D0%B4%D0%B2%D0%B8%D0%BD%D1%81%D0%BA_(%D0%90%D0%9F%D0%9B).jpeg

Typhoon has ducted screws: https://battlemachines.wordpress.com/tag/soviet-submarines/

An incredible article "The Taming of the Screw" !!!: http://americanhistory.si.edu/subs/anglesdangles/taming.html

If only the 'Does not cavitate' flag actually meant something as far as the code was concerned.