Yep, that's why
https://www.subsim.com/radioroom/sho...postcount=3834
Kilos could be transported on swimming platforms to the black sea, they did that before. For all bigger subs .. not sure but unlikely.
Regarding bridges it depends on the river, there is one of the two that has high cliffs on one side while being flat on the other, i take it most ships would be able to navigate there, choosing the side of the undercut bank and the bridges being high enough on that side.
Do you think there is any possibility to find a Kilo in the black sea. Not Ukraine.. how about Bulgaria, Turkey?
Are drones suited for this task?
I guess a Bayraktar TB x would not be able unless the sub would be surfaced, and it cannot carry enough ordnance to destroy it. I am not informed of the capabilities of a "global hawk" though.