Poland has an ideal device for this sabotage

https://www.gospodarkamorska.pl/zdjecia/artykul/25081/135779...

Why does everyone assume the need for submersibles? Why not a small patrol boat dropping some depth charges on a time delay in the middle of the night?

> patrol boat dropping some depth charges on a time delay in the middle of the night

That's also an option, but you would have problems with precision and deniability*.

You could use some WW2 style device and blame it on German mines that are still present.

I'm not sure deniability is so important when it's multiple coordinated explosions.

How else could it have been done.. What about explosives being built in from day 0? Sort of like how some bridges in Europe were pre-mined during the cold war?

by deniability I mean that you cannot be sure if this is Russia, USA or someone else. If you use depth charges, they explode in certain way and leave some debris which say "this was XXX bomb so must be Russia/USA".

This is sabotage for sure.

It’s a pretty overt act to blow both up. Someone was making a statement

If you knew the exact position of the pipes, why would there be a problem with precision? Maybe there are lighthouses in sight which you could use to line up exactly, maybe you'd use gps/glonass, maybe you'd have some plane go by near at a specified time, doing it for you, saying via radio, all good, drop it?

Water currents could be one cause of inaccuracies

How much does an object drift in 100m of water and how accurate do you need to be?

If it was actually used this way I'll:

1. Eat my hat.

2. Go out and protest.

It would have been quite the new low, even for the current establishment.

Follow up:

It might have been a drone:

https://nyheder.tv2.dk/udland/2022-09-27-norge-advarer-om-my...