Complex sentence: It is the only sea on Earth which has no coastline; a distinctive body of water with brown "Sargassum" seaweed and calm blue water, very different from the rest of the Atlantic Ocean.
Split into simpler sentences: It is the only sea on Earth which has no coastline. A distinctive body of water with brown "Sargassum" seaweed and calm blue water, it is very different from the rest of the Atlantic Ocean.