German investigators' earlier theory was that a small team of perpetrators used a rented 50-foot sailboat, the
Andromeda, to plant explosives on the two pipelines. But as their investigation progressed, they began to suspect the boat might have been used as a decoy, and U.S. and European officials are also now skeptical that the
Andromeda played a key role. One major reason for the doubt is the craft's size and capabilities, per the
Post:
"Experts noted that while it was theoretically possible to place the explosives on the pipeline by hand, even skilled divers would be challenged submerging more than 200 feet to the seabed and slowly rising to the surface to allow time for their bodies to decompress. Such an operation would have taken multiple dives, exposing the
Andromeda to detection from nearby ships. The mission would have been easier to hide and pull off using remotely piloted underwater vehicles or small submarines, said diving and salvage experts who have worked in the area of the explosion, which features rough seas and heavy shipping traffic."
Also according to the
Post, investigators have confirmed that traces of military-grade explosives found during a search of the
Andromeda in January matched the explosive used on the pipelines — but that the evidence might have been planted aboard the boat. Some investigators also doubt that a team skilled enough to blow up the pipelines while evading detection would be sloppy enough to leave that evidence behind, while others believe it was possible they were indeed that careless."