Submarine networks are the main interconnecting infrastructure between all continents. As so, they transport an enormous volume of traffic being an active part of the global backbone network topology. As Space Division Multiplexing (SDM) promises to provide the so wanted extra bandwidth in optical communications, its potentials regarding submarine networks have to be investigated. Apart from connecting far away located continents or regions, submarine networks can be also utilized as a backup to terrestrial networks especially in closed seas or long coastlines. In this paper we discuss all new technologies applied in optical submarine networks and we design an all new SDM-based submarine optical network for Greece. The proposed design is based on well known redundancy and performance objectives applied in backbone networks. Moreover, we extend in the economics region and conduct a detailed cost analysis of the proposed design. The economic analysis enables us to spot on design issues in which costs can be significantly reduced.