English: Along its southeastern coasts, the Caspian Sea is often marked by colourful swirls of permanently turbid water. The area in which these sediment plumes form is referred to as “marine shallows” and is under 30 meters deep. The geometry of floating sediments strongly depends on weather conditions. In this Copernicus Sentinel-3 image captured on 2 September 2020, besides floating sediments in the marine shallows, various sediment swirls that have formed in the last days of August along the southern Iranian coast (bottom of the image) are visible. Their formation was caused by strong winds that moved the sediments along the coast causing a sequence of swirls in a clockwise expansion pattern. The Copernicus Sentinel-3 mission, which is composed of two twin satellites, Sentinel-3A and Sentinel-3B, is equipped with a specific optical sensor, called the Ocean Land Colour Instrument (OLCI) that allows to measure ocean colour and gather information about marine biological constituents. For coastal and shallow waters, the colouration of waters can also result from the release of ground water loaded with suspended sediment and organic matter, as well as re-suspension due to wave agitation. Initially designed for research studies in marine biology and the carbon cycle, this observation technique has spawned several applications towards marine area management and coastal zone management.