Soviet Akula- Class nuclear submarine
 

Rather than submerged in an ocean of air, like our cars, the Akula-Class, fastest for it's reactor type, is a study in hydrodynamic efficiency, submerged in something more than 800-times more dense than what our cars 'swim' through.
https://www.youtube.com/watch?v=cF9bubcXB2o

Akula 'sail / conning tower'
 

Some of you may notice that the sail 'on top of' the Akula sub has a striking resemblance to some control cars 'underneath' the great airships of the 20th-Century.
And it's no fluke, just good design.

They don't show the propeller except that model at 4:11. Possibly the skewback screw?

Submarine Secrets: Pump Jets And Propellers Explained

propellers / propulsors
 

These are state secrets. They're kept under wraps during manufacture and launch.
Other than those on the authorized access list, only NAVY SEALs and SOVIET 'SEALS' have ever seen them. And what they've seen must be taken to the grave.

So, don't look?

I thought you might be interested in the four-fin vortex generator on the seven-blade prop. It's right in the thumbnail.

Vortices make sonar reflections. Bad juju in sub warfare. I suspect they are anti vortex.

look
 

I'm kinda busy saving the world.
Hydo-accoustics doesn't play into that, best I can tell.
Although, my freedom to ponder saving the world comes at the expense of eyes-only military secrets and all-volunteer military service.

Bad juju
 

Anti-cavitation as well. Collapsing water vapor bubbles shed from a propulsor would have a horrific acoustic signature.
It escalated the Vietnam War, when the electronics officer aboard the U.S.S. Vincennes detected the sound of his own screws, and it was reported to Washington D.C. as a hostile torpedo attack from N. Vietnam.
All Lyndon Johnson needed.

Well, I'm certainly not going to watch the video again to find out, now that I know Youtube is disseminating Russian State secrets.

PBCF (Propeller Boss Cap Fins)