Two of the many islands that make up the Bahamas, a British possession, are highlighted in this near-vertical photograph—Crooked Island to the northwest, separated by the Bight of Acklins from Acklins Island, the elongated, eastward island. The Bahamas comprise a dramatic combination of carbonate banks, islands, and deep water channels that have built up during the past 70 million years. Coral and algal reefs abound in the warm, shallow water. The strikingly different shades of blue provide a wealth of information about the water—the lighter shades, for example, show a variety of features within the very shallow waters, including constantly changing small banks, channels, ripples, shoals, grass, and algal beds. The dropoff from the shallow depths of generally less than 50 feet (15 meters) to depths exceeding 1000 feet (300 meters), represented by the darker blue, is abrupt and precipitous. Clarity of the water throughout the Bahamas primarily results from their distance from continental sediment sources. These two islands have not experienced the fairly rapid economic, tourist-related growth that many of the other Bahamas have experienced; however, several roads and two airport runways are visible.