Definition:
The country in which the effective centre of the sea transport carrier/operator's commercial activity is located.

Source:

• Directive 2009/42/EC of the European Parliament and of the Council of 6 May 2009 on statistical returns in respect of carriage of goods and passengers by sea
  Place of publication: (Dz. Urz. UE L 141 z 06.06.2009, str. 29, z późn. zm.)