Data availability is of vital importance for marine research but most of the European data are fragmented, not always validated and not easily accessible. In the 40 countries bordering the European seas, more than 600 scientific laboratories from governmental organizations and private industry collect data by using various sensors on board of research vessels, submarines, fixed and drifting platforms, airplanes and satellites to measure physical, geophysical, geological, biological and chemical parameters, biological species etc. SEADATANET aims to develop an efficient distributed Pan-European Marine Data Management Infrastructure for managing these large and diverse data sets. The objective is to network the existing professional data centres of 35 countries, active in data collection, and provide integrated databases of standardized quality on-line. The on-line access to in-situ and remote sensing data, meta-data and products will be provided through a unique portal interconnecting, in the first phase, 11 interoperable node platforms. The development and adoption of common communication standards and adapted technology will ensure the platforms interoperability.