Wikimedia
Wikipedia: Specific Gravity
Wikipedia offers a brief explanation on what specific gravity is and why it is measured in terms of density of water. The equation for its measurement is also given.
Texas Education Agency
Texas Gateway: Ap Physics: Fluid Statics: Archimedes' Principle
By the end of this section, you will be able to define buoyant force, state Archimedes' principle, understand why objects float or sink, and understand the relationship between density and Archimedes' principle.