The Sentinel-3 satellite hosts a suite of sensors designed to study our oceans. The Ocean and Land Colour Imager provides ocean colour images. From these images we can estimate the chlorophyll content of the water column, in order to study plankton distributions and get information on algal blooms.
S3 also carries an altimeter, which has a dual role for ocean studies. It measures the height of the sea surface, from which currents can be estimated, but also the wave heights.
Finally, the Sea and Land Surface Temperature Recorder (SLSTR) provides sea surface temperatures, which are vital for weather and climate forecasting.