Arc Marine: GIS for a Blue Planet presents the initial results of a successful effort to create and define a data model for the marine community. The data model not only provides structure to storing and analyzing marine data but also helps users create maps and three-dimensional scenes of the marine environment in ways invaluable to decision making. The standards and best practices that emerge from the case studies in Arc Marine form a diverse set of resources to draw from as the marine community strives to understand, illuminate, chart, and explore the unknown depths.