The sea was first named by the ancient Greeks who called it "Inhospitable Sea." The sea got this reputation because it was difficult to navigate, and hostile tribes inhabited its shores. Later, after the successful development of the coast by Greek colonists, the sea was renamed "Hospitable Sea." A popular hypothesis about the origins of the Red Sea's name is that it contains a cyanobacteria called Trichodesmium erythraeum, which turns the normally blue-green water a reddish-brown.