They’d ram one torpedoes of these up the Chesapeake Bay and swamp everything from Newport News to Washington with cobalt-60 contaminated water.
We likely have something similar and haven’t made it public.
Status-6 Oceanic Multipurpose System
The Poseidon (Russian: Посейдон, “Poseidon”, GRAU index 2M39, NATO reporting name Kanyon), previously known by Russian codename Status-6 (Russian: Статус-6), is an autonomous, nuclear-powered unmanned underwater vehicle reportedly in production by Rubin Design Bureau, capable of delivering both conventional and nuclear warheads.
https://en.wikipedia.org/wiki/Status-6_Oceanic_Multipurpose_System
Creepy stuff.