How deep was the water?
That may reduce the possibilities...
50-100 meters for most of the run of the pipelines from what I can see..
Thats 25-50 fathoms. The Baltic is shallow.
That may reduce the possibilities...
Depth is moderate, in the neighborhood of 250-320 feet. A surface boat could launch an ROV carrying a shaped-charge mine for delayed detonation.
I heard a semi-credible report that we had an amphibious task force in that area a few days ago. When you think about it from several different angles the end point is the same.
The EU, in particular Germany (the cornerstone of the EU) is not lately a good friend to us nor are we to it. We have no love lost for Russia either. The destruction of NS-1 and NS-2 screws them all while increasing demand for US LNG.
The US had motive and certainly had opportunity.