Why is it called the Dead Sea? The sea is called "dead" because its high salinity prevents macroscopic aquatic organisms, such as fish and aquatic plants, from living in it, though minuscule quantities of bacteria and microbial fungi are present. In times of flood, the salt content of the Dead Sea can drop from its usual 35% to 30% or lower.
Why do you float in the Dead Sea? Since you are lighter (less dense) than water, the water pushes you up enough foryou to float. The Dead Sea has a LOT of salt in it. Salt water is heavier (denser) than regular water. People can float in regular water, but since salt water is even denser, it is even easier to float in the Dead Sea.
The Dead Sea is the deepest landlocked salt lake in the world, and its extreme levels of saline means it cannot sustain animal life — hence the name. Because of the high density of the water, swimming in the lake is more like floating on the top of the water.