Several marine data portals do exist, an uncomplete list is provided below:
GMIS – Global Marine Information System
This system provides bio-physical information for water quality assessment and resource monitoring in the coastal and marine waters. The environmental data in GMIS mainly relies on Earth Observation data, and the provision of continuous, detailed and accurate information (gmis.jrc.ec.europa.eu)
GMED
Global Marine Dataset for species distribution modelling and environment visualisation, data released under the OpenSource licence GPL (gmed.auckland.ac.nz/data.html)
Ocean exploration, remote sensing, biogeography lab
Download links to a variety of data sets (sea surface temperature, chlorophyll etc.) by the University of Delaware (orb.ceoe.udel.edu/public-access)
EMIS – Environmental Marine Information System
This system provides simple and user-friendly mapping of geo-referenced maps created in realtime, and supplies the users with basic navigation and interrogation tools for regional assessment. It mainly focus on European data (emis.jrc.ec.europa.eu)
Ocean Colour Portal
The Global Environment Monitoring Unit is maintaining an archive of ocean colour derived products for the European seas, over the geographical domain 40W-55E, 10N-80N (oceancolour.jrc.ec.europa.eu/data_portal/oc_portal)
Coral Reef Watch Satellite Monitoring
NOAA’s Coral Reef Watch Program’s satellite data provide current reef environmental conditions to quickly identify areas at risk for coral bleaching (coralreefwatch.noaa.gov)
NASA Earth Observation
Nive page to browse and download images as well as spatial data sets of global products such as water vapor, temperatue, net radiation etc. (http://neo.sci.gsfc.nasa.gov)