The route was cleared of what Tennet called an "unexpectedly large quantity of old munitions" over an 18-month period at a "high cost" to the transmission system operator.
Remotely-operated underwater vehicles, submarine magnets and other devices were used during the clearance, in addition to divers.
Almost 30 tonnes of explosives were retrieved and disposed of before the Lower Saxony munitions disposal service judged that it was safe to lay the cables.
The submarine cable section has been wound on to the Bodo Installer cable-laying vessel in Emden, north-west Germany, ready to be laid once a trench has been preflushed.
Tennet said that it predicts that the connection will be completed at the beginning of 2014 due to "the continued unpredictability of the weather".