False.
Very few countries have the technical capability to pull that off, and the Ukraine is not one of them.
“Very few countries have the technical capability to pull that off”
Be specific. Why couldnt a few commercial divers with current equipment (modern underwater gear, sonar, gps, etc) go down 200ft to plant modern military explosives rigged as time bombs?
You are waving off the real sophistication that is commercially available and is SOP in the daily processes of industry.