Those are some serious arguments, Bill. So '8000yds, 28kts' are parameters of the torpedo ? Those are mentioned anywhere on the net.
But it can be clearly seen on pictures that CAPTOR itself has no propeller. Only the torpedo inside has one.
http://www.navweaps.com/Weapons/WAMUS_Mines.htm
Such weapon has even less usage options in DW I guess.
PS: how long can CAPTOR stay on watch ? I didn't find it mentioned anywhere. I know it has fuel-based energy plant, nothing more.