At more than 1,000 feet below sea level, the Dead Sea is the deepest lake in the world. Once connected to the sea - hence the salt - this lake between Israel, Jordan and the West Bank is so dry that it loses water rapidly, more than three feet per year. Today the concentration of salt in the water is about 33 percent, which causes it to crystallize on shore. For diving this environment, you need a full-frame mas and lots of weights. Swimming it is easier, but you still don't want to get even a drop of water near your eyes.
Dead Sea Divers deadseadivers.com