Density and Specific Gravity

Density and Specific Gravity
These ship terms are more to do with Tanker Officers and Crew.
Density, by definition, is the amount of matter per unit of volume. Or, more simply, mass over volume. Hence it has units of kg/cm3.
E.g. the Density of Sea Water is approx. 1025 kg/m3
Specific Gravity is a ratio of the density of the substance divided by some reference material, typically Fresh Water. The units cancel each other out, often referred to as a ration.
For E.g. the Specific Gravity of Diesel Oil is 0.86
Density and Specific Gravity are the same if the reference material is Fresh Water since the Density of Fresh Water is 1.0 kg/cm3.