For instance, the Ukrainian individual who informed the European intelligence service in June said that six members of Ukraine’s special operations forces using false identities intended to rent a boat and, using a submersible vehicle, dive to the floor of the Baltic Sea and then damage or destroy the pipeline and escape undetected. In addition to oxygen, the team planned to bring helium, which is recommended for especially deep dives.
German investigators now believe that six individuals using fake passports rented a sailing yacht in September, embarked from Germany and planted explosives that severed the pipelines, according to officials familiar with that investigation. They believe the operatives were skilled divers, given that the explosives were planted at a depth of about 240 feet, in the range that experts say helium would be helpful for maintaining mental focus.