Today the Dead Sea is 411 m below sea-level, which makes it the lowest point on the earth’s surface. Fifty thousand years ago it was a much bigger lake, ad its surface was 225 m above the present level. Even at the beginning of this century the sea was 12 m higher than it is now. The dropping water-level caused the length of the sea to decrease from 70 km to 50 km in 1976, when the lynch Straits dried out. The ford linking the Lisan (HaLashon) to the west bank would be passable for the first time since the early C19 were it not for the new canal bringing water to the salt-pans at Sedom.
Such variation is directly related to the amount of rainfall. In recent times the volum of water coming into the Sea has been further reduced by pumping from the Sea of Galilee and from the Yarmuk river. There is a plan to dig a canal from the Mediterranean in order to prevent the sea from drying up completely.
The sea has no exit and water is lost only through evaporation, in summer as much as 25 mm in 24 hours. This produces a concentration of all chlorides (magnesium, sodium, calcium, and potassium) in the water (275 g per litre). It is possible to swim in the sea at EinGedi and at EinBoqeq; a shower is essential immediately afterwards to wash off the salt. Being nearly several times as dense as ordinary sea water, one can sit in it and read a newspaper comfortably. But while it is impossible to sink, water in the lungs is fatal. Enter the water slowly and cautiously. Do not dive or put the head under water.
Source: The Holy Land by Jerome Murphy- O’Connor