Every substance, body or material has mass and volume, however the mass of different substances occupy different volumes.
This is where density [tex]D[/tex] appears as a physical characteristic property of matter that establishes a relationship between the mass [tex]m[/tex] of a body or substance and the volume [tex]V[/tex] it occupies.
[tex]D=\frac{m}{V}[/tex]
So, according to this equation, the density is inversely ptoportional to the volume:
If the volume increases, the density decreases.
This is what a fish does to have buoyancy, since the density of a body is related to its buoyancy:
A body will float on another fluid if its density is lower.
