https://www.atlanticcouncil.org/in-depth-research-reports/re...
Finland and Estonia share a 1GW electrical interconnector (composed of two HVDC submarine cables, with a signed MOA for a third) Estonia is using to consume power from Finland's recently turned up nuclear generator. I am unaware if it is buried, but it is a strategic critical infra asset that likely requires defense.
Its easy to overthink these problem spaces (imho), but I propose that Russia's current geopolitical posture adds an element of a wildcard necessitating the thought exercise. This infra can take months to build or repair, but only hours to cripple.
https://en.wikipedia.org/wiki/Estlink
https://app.electricitymaps.com/zone/EE?wind=false&solar=fal...
Example commercial system: https://electronica-submarina.com/protection-of-critical-inf...
Example US Navy military system SOSUS: https://en.wikipedia.org/wiki/SOSUS (which is suspected to be what detected the Titan submersible implosion)
These cables are often deliberately laid far enough apart that, should they need to be serviced, they can be hauled up by dragging an anchor/hook until it snags the correct cable. So it is equally not difficult to attack a chosen cable with nothing more complex than an anchor, a long chain, and a handheld GPS.
Except for the constant threats of nuclear Armageddon, the sabotage of the Bulgarian munitions factory, ramming into a US drone over the Black Sea, shooting a missile at a British jet over the Black Sea, threatening to invade Gotland, threatening to invade Poland, violating Finnish, Swedish, and Norwegian airspace. I’m probably forgetting some things, it’s been a long war.
I'm 99% sure that all the cables have been identified and if the order is given, they will be cut. Along with all other infrastructure.
At least not for state actors, or perhaps well-funded terrorist groups.