The main aim of the article is modelling the operation process of the Baltic Port, Shipping and Ship Traffic and Port Operation Information Critical Infrastructure Network. To achieve this goal it is necessary to define three critical infrastructure networks for a Baltic Sea Region and their operation processes: port critical infrastructure network, shipping critical infrastructure network and ship traffic and port operation information critical infrastructure network. Thus, the concept of networks of three networks, called Baltic Port, Shipping and Ship Traffic and Port Operation Information Critical Infrastructure Network, is introduced. This way, the operation process of network of networks is proposed. To understand this approach, the basic classification and description of interdependencies and interconnections in this network are presented.