![](\"http:\/\/www.esa.int\/var\/esa\/storage\/images\/esa_multimedia\/images\/2015\/10\/deep_blue_red_sea_reefs\/15642029-1-eng-GB\/Deep_blue_Red_Sea_reefs_small.jpg\")
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\nThis beautiful true-colour image features the Red Sea coral reefs off the coast of Saudi Arabia.\n<\/p>\n
\nThis vast, desolate area in the very northern corner of the Red Sea is bordered by the Hejaz Mountains to the east. The area was once criss-crossed by ancient trade routes that played a vital role in the development of many of the region\u2019s greatest civilisations.\n<\/p>\n
\nToday, the Red Sea separates the coasts of Egypt, Sudan and Eritrea to the west from those of Saudi Arabia and Yemen to the east.\n<\/p>\n
\nIt contains some of the world\u2019s warmest and saltiest seawater. With hot sunny days and the lack of any significant rainfall, dust storms from the surrounding deserts frequently sweep across the sea. This hot dry climate causes high levels of evaporation from the sea, which leads to the Red Sea\u2019s high salinity.\n<\/p>\n
\nIt is just over 300 km across at its widest point, about 1900 km long and up to 2600 m deep. Much of the immediate shoreline is quite shallow, dotted with coral reefs along most of the coast \u2013 making excellent diving spots in many areas.\n<\/p>\n
\nIts name derives from the colour changes in the waters. Normally, the Red Sea is an intense blue\u2013green. Occasionally, however, extensive algae blooms form and when they die off they turn the sea a reddish-brown colour.\n<\/p>\n
\nThe Red Sea lies in a fault separating two blocks of Earth\u2019s crust \u2013 the Arabian and African plates. \n<\/p>\n
\nNavigation in the Red Sea is difficult. The shorelines in the northern half provide some natural harbours, but the growth of coral reefs has restricted navigable channels and blocked some harbour facilities.\n<\/p>\n
\nShallow submarine shelves and extensive fringing reef systems rim most of the Red Sea, by far the dominant reef type found here.\n<\/p>\n
\nThe lighter blue water depicted in the image means that the water is shallower than the surrounding darker blue water.\n<\/p>\n
\nFurthermore, water clarity is exceptional in the Red Sea because of the lack of river discharge and low rainfall. Therefore, fine sediment that typically plagues other tropical oceans, particularly after large storms, does not affect the Red Sea reefs.\n<\/p>\n