Floating in salt water and fresh water
Why is it easier to float in salt water than in fresh water?>
When anything floats, it is because the vertical forces acting on it sum to zero. Sir Isaac Newton told us this in his Third Law of Motion.
Objects feel a downward force due to their weight. The balancing upward force on an object in a fluid is called a buoyant force. Archimedes is credited with the first understanding that the buoyant force is equal to the weight of the fluid that is displaced. On average, sea water is 3% denser (more mass per unit volume, thus more weight per volume) than fresh water, so less of it must be displaced to provide a buoyant force sufficient to balance the weight of the object. This is why floating is easier in salt water than in fresh.