The pipelines are only about 210 feet down at that point so it would have been accessible to divers without much difficulty.
The thing that has me the most concerned is that the Balt Pipe pipeline was also damaged. This carries gas from the North Sea across Denmark to Germany. Somebody, I don't know who, has decided that energy infrastructure is now a legitimate sabotage target.
The people I LEAST suspect are the Russians and the Germans since they are they ones most hurt by the attack. Russia had already voluntarily turned off Nord 1. They will eventually want all 4 pipelines in operation so they can earn money, which they need. Poland, Finland, Sweden, Lithuania, Latvia, Estonia, and the US are only marginally more likely. All would like to see Russia taken down a peg but I doubt they would hurt the Germans so badly to do it. The Ukrainians are likely suspects. They certainly have the motive but there are much easier targets that they still haven't attacked.
I can't get the thought that it might be some fringe Eco group. Where they would get the means I'm not sure.
At this point the German economy is on life support. They absolutely depend on Natural Gas as feed stock for their industry. It's going to be a dark cold winter in Germany.
WWG1WGA
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)