Dead Sea Uncovered

The Dead Sea has a salt concentration of about 34% — roughly ten times saltier than typical ocean water. All that dissolved salt makes the water far denser than fresh water, so it can support more weight before an object sinks into it.

The result: you float effortlessly, bobbing like a cork. It's nearly impossible to swim normally because your limbs keep rising to the surface. This same principle is why it's easier to float in the ocean than in a freshwater pool.