In English units, the density of water is 1.936 slugs per cubic foot. A slug is different from a pound because the slug measures the mass of a unit, but a pound measures the force of the unit in relation to gravity.
It is important to note that a slug is not a commonly used unit when referring to the density of objects, even in the United States measuring system, because it is much easier to use the kilogram system for finding the density of objects. The slug makes the process more complicated and is easily confused with pounds because they are closely related.
The density of water is dependent on the slugs per unit, or the kilograms per unit. Units are generally measured in a way of cubic feet or cubic meters, if the metric system is being used.
There are many reasons why the density of something may be used, but the most common reason is to determine whether a substance will be able to float. Things that are less dense than water are generally not able to float, while things that are denser than water are able to float. Hot water is not able to float because it is the same as water and technically already floating, but frozen water is able to float because easily it has a higher density to it. All substances carry a different density due to the different properties of the substances.