The General Bathymetric Chart of the Oceans (GEBCO) aims to provide the most authoritative, publicly-available bathymetry data sets for the world’s oceans.
To find high-quality online resources including maps, visit the University of Wisconsin Scout Report's sister site: AMSER, the Applied Math and Science Educational Repository at http://amser.org. These are free materials for the classroom or personal education.
From a webpage entitled: "About the Oceans", from the National Atlas of Oceans: Maps and Statistics and Online Databases: a collection of maps, statistics and databases related to oceanic geography, islands, continental shelves, ocean depths, troughs and deeps, sea beds
