[toomuchtodo]

You can bury them deeper after being laid in trenches created using undersea ploughs or water jets. They will always be vulnerable where they came to shore though, unless you're going to bury them deep all the way to the equipment hut on the shore. There is undersea concrete available for vulnerable paths (both articulated blocks and a mix that can be grouted and will set underwater), but I believe that likely draws more unwanted attention to the asset's route without providing much more protection.

https://www.atlanticcouncil.org/in-depth-research-reports/re...

https://www.youtube.com/watch?v=d9tRmJLOCdg

[tivert]

Those seem like a defense against accidental damage, but I don't see how burying a cable in a shallow trench or covering it with a few blocks of concrete will protect it from a "bad actor."

[toomuchtodo]

Absolutely, boils down to your threat model. If you are defending against a nation state actor, you are probably going to want to deploy underwater surveillance across the cable's length and station folks who can respond when someone nefarious shows up to chop chop. No security is absolute, you are either dissuading or slowing down an attacker based on their resources and available window of time. It's 42 miles/67km from Finland to Estonia across the Gulf of Finland, which does not seem challenging to defend vs cables crossing oceans. Sweden to Estonia is definitely a bit further.

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)

[sandworm101]

The bad actors aren't down there with shovels and robots digging down into trenches. They are just like any other ship dragging an anchor across the bottom close to the cable.

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.

[algorias]

The places where these cables come to shore are rightfully rated as high-priority military targets. You can't just walk up to them, nor go poking around in a yacht.