The Dead Sea is known for the wonderful properties of it’s mineral-rich waters. The waters are used to produce a huge variety of health and beauty products that are sold all over the world.
According to the Jewish viewpoint, when G-d destroyed the city of Sodom and its sister cities in the book of Genesis, the Jordan plain became an enormous crater. This crater was filled with the waters of the Jordan River running into it and the minerals from the earth combined with the waters to form what is now known as the Dead Sea.
Ezekiel prophesied that the day will come when the waters of the Dead Sea will be sweetened and people will fish along its shores. The waters will be sweetened by waters that will flow into it from the rebuilt third Temple. Along the banks will grow fruit trees of every imaginable type that will never wither. The fruits on the trees will be ripe month after month due to the trees’ water source being waters that come from the Temple. The fruit will cure those that eat it.
According to mystical Jewish teachings, these miraculous occurrences have deep meanings behind them. We learn in the book of Genesis that on the second day of creation G-d separated between upper and lower waters. According to the Midrash, when this happened the lower waters cried that they too wanted to be in G-d’s presence.
Water, in mystical teachings, symbolizes pleasure. There are also two types of pleasure. There are the upper waters that refer to spiritual pleasures that souls and angels experience and the lower waters that represent earthly pleasures found in the physical world. The lower waters were crying for the fact that they were condemned to a life lacking spirituality.
The bitterness voiced by the lower waters is hinted to in salt water, tears of sadness and specifically in the saltiest body of water; the Dead Sea.
It is the goal of each and every human being on this earth to elevate this lowly world into a place where G-d can dwell. Through this elevation we are essentially sweetening the lower waters. When this is fully accomplished we will merit to witness the era of the Messiah-
Mashiach in Hebrew- and in such an era all of mankind will merit to be spiritually uplifted to beyond even the level of the upper waters.
The future sweetening of the Dead Sea as described by Ezekiel is symbolic of the healing process that the entire creation will undergo, G-d Willing in our times.
Taken from http://www.chabad.org/special/israel/points_of_interest_cdo/aid/588229/jewish/Dead-Sea.htm