NETMAR aims to develop a pilot European Marine Information System (EMIS) for searching, downloading and integrating satellite, in situ and model data from ocean and coastal areas. It will be a user-configurable system offering service discovery, access and chaining facilities using OGC, OPeNDAP and W3C standards. It will use a semantic framework coupled with ontologies for identifying and accessing distributed data, such as near-real time, model forecast and historical data. EMIS will also enable further processing of such data to generate composite products and statistics suitable for decision-making. NETMAR will develop interoperability and connectivity between heterogeneous data systems to meet the demand for information from different user groups. Standardising data and metadata formats, as well as exchange protocols, are the first steps to bridge existing marine data systems. The next step is to define the semantics of the services, including an uncertainty model, to allow transparent computer-based discovery. Developing a semantic framework for marine data services, backed by a multilingual and multidomain ontology enabling searches across (human) languages and application domains, is therefore a key task. EMIS will enable search for and use single services, as well as to compose new and more powerful services by service chaining, defining the workflow of the composite service using existing services as "building blocks". EMIS will then merge established standards and tools with these new "building blocks" for application in practical monitoring of the marine environment. This will be done through a set of use cases in different European seas, where identified users will test and evaluate the EMIS. The use cases include monitoring and forecasting of oil spills, plankton blooms and Arctic sea ice. Furthermore, the use cases will validate an ecosystem model, study the relation between physical and biological variables and data exchange with coastal web atlases.