The Dead Sea found on the borders of Israel and Jordan is the world's saltiest and densest body of water. First, it's completely landlocked, so any fresh or saltwater that flows into it from the Jordan River and other tributaries (estimated at six and a half million tons per day) is trapped – until it evaporates.

Evaporation happens quickly because that portion of the world is extremely hot, leaving the salt behind. The concentration of salt in the water is so high that the only living things that can make their home there are bacteria. When the water evaporates, the salty minerals are left behind, causing the remaining water to become more and more concentrated with salt.

Since human bodies have a lower density than the water of the Dead Sea, people can float in it effortlessly. The extremely salty water holds people up instead of letting them sink.