Specific Gravity of Water
Why We Can Float in Water
- Specific gravity is defined as the ratio of the density of a substance to the density of water.
- Water has a specific gravity of 1.0: any object with a specific gravity less than 1.0 will float in water and anything with a density greater than 1.0 will sink.
- The human body has a density slightly less than that of water and averages a specific gravity of 0.974, therefore we float.
How Fat and Muscle Affect the Ability to Float
- Lean body mass, or the mass of the body minus the fat, has a typical density near 1.1, whereas fat mass has a density of about 0.9. Therefore, an individual who has a high percentage of lean body mass may require floatation devices.
- In contrast, an obese individual will have a specific gravity considerably less than 1.0 and will float more easily.