What body of water is the second cataract of the nile river submerged under

The Cataracts of the Nile are shallow lengths (or white water rapids) of the Nile River, between Aswan and Khartoum, where the surface of the water is broken by many small boulders and stones jutting out of the river bed, as well as many rocky islets. In some places, these stretches are punctuated by whitewater

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