SASLess, having been to Kronstadt it would have been a whole lot more of hurt than tapping an undersea cable.
The water is very shallow, entrance, the 'deep' water channel is between the mainland and the fortress about 2-3 miles wide. It was, incidentally, the penetration route for one of our targets.
WUH, I did the WEC at Cranditz in 1974 and the Nike in the SSM role was one option and indeed the weapons of choice for our exercise target. It would have had the benefit of collateral damage on the adjacent town.