Back in '77 when I interviewed for an engineering position with Electric Boat in Groton, the subs under construction all had shrouds over their props. The guys interviewing me freely said the prop designs were secret, and that the shrouds were there simply to help thwart surveillance, by satellite or otherwise. No big mystery why they're there.

This is the most content-free video on YouTube. Not once did you explore the "weird reason" the US navy does not display submarine propellers openly. No, our navy does not hide propellers to protect them from harm, so much as to keep Russian and Chinese intelligence from direct observation of the submarine's propulsion design-- type of propeller and thruster assembly. The video was so superficial, we decided not to subscribe.

Im a retired Marine from the nam days. I was on a Med cruise with the 6th Fleet in 1972. I was on the LPD12 USS Shreveport. Standing on the helo deck near the fantail,I saw a small trailing disturbance in the water about a hundred yards off our starboard side.I asked the sailor on the catwalk with headphones on what it was. He said it was a Soviet subs periscope.Been hanging around us for 3 days. It was kinda cool in a way...two superpowers engaged in cat and mouse,LOL.Just glad it was each of our ships involved in maneuvers rather than hunter killer attacks.

I wonder if we'll see magnetic propulsion or articulated swimming tails on submarines. I guess as drones-subs become more feasible and sophisticated, the naturalistic design process using supercomputers will produce really weird looking craft in future.