Surely they're not retarded enough to sail a sub into such well defended waters.There's lots of rumors, the one I heard is a Seawolf-class has been bottled up in Bohai.
Given the size of Seawolf and depth of Bohai I think we can dismiss that out of hand to be on the same level as Ghost of Kiev or 052D lurking off the coast of California.
In before all the jokes about "Blue October" and how the Seawolf XO would like to have two Chinese wives cooking rabbits for him.
It'd just get surrounded by navy/coast guard and the sea floor and end up looking like that container ship that got stuck in the suez canal