Isn't salt water & fresh water a somewhat different density? Hence submarines bouncing off holoclines (I think that's the word)... And getting sunk.
If the seals on the bearings are marginal for sea water won't they leak like a sieve when they've got fresh water running through them, more to the point why would you pull water from outside into them when people will possibly be firing at you, one hit in the wrong place, cooked bearings and you're dead in the water.
This thing seems to be about as bright an idea as a liquid sodium reactor, a device that made the Chernobyl style reactors look fantastic. I mean what could possibly go wrong with a reactor coolant that explodes in fresh air, explodes even more in water and leaks more readily than a Royal Oilfield or Driptroit Diesel.
Given some of the stuff that's been designed recently, recent election results, and other bright ideas (electric cars, when our electricity grid was designed by Lucas) I am beginning to think humanity has reached peak fsckwit.