Liquids that are lighter than water have a specific gravity that is:

Liquids that are lighter than water have a specific gravity of less than 1. Specific gravity is a measure of the density of a substance compared to the density of water. Since water has a specific gravity of 1, any substance with a specific gravity lower than that will float on water. Therefore, when a liquid has a specific gravity less than 1, it indicates that it is less dense than water, hence causing it to be buoyant and float. This property is crucial in various applications, such as firefighting, where understanding the behavior of different liquids in relation to water is essential for safety and effective response measures.