DEAD SEA — It is an unparalleled wonder of the world: the lowest exposed spot on Earth, its therapeutic waters are so full of salt that bathers float right to the top. This natural spa is a source of rich minerals used by the ancient Egyptians for mummification, and fabled to be the biblical site of Sodom and Gomorrah. / Ofir Berman for NPR / Ofir Berman for NPR Gregory, a recent immigrant from Russia, floats in the Dead Sea at a beach connected to an Israeli hotel resort on Nov. 10. The water of the lake is so full of salt that bathers float right to the top. /…