The amount of "squishing" is what we call the compressibility of water. In a weightless environment, this squishing wouldn't occur, and the water would be slightly less dense. However, the compressibility of water is very low, which means that the water doesn't squish very much under its own weight; as a result, its density in space would be ...

Table of Properties of water at varying temperatures and Saturation Pressure Note : Isothermal compressibility β (1/MPa) = 1/K ...(K=Bulk Modulus). For liquid this is virtually the same as the isentropic compressibility. For vapours it is not the same as isentropic compressibility ref Compressibility 1000 Pa-s = 1 cP

In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility [1] or, if the temperature is held constant, the isothermal compressibility [2]) is a measure of the instantaneous relative volume change of a fluid or solid as a response to a pressure (or mean stress) change.

Example 27.3: Compressibility of Water. Determine the percentage decrease in a fixed volume of water at a depth of 4 km where the pressure difference is 40 Mpa, with respect to sea level. Solution. The bulk modulus of water is \(2.2 \times 10^{9} \text Pa\). From Equation \ref{27.5.3},

Compressibility is the measure of the change in volume a substance undergoes when a pressure is exerted on the substance. Liquids are generally considered to be incompressible. For instance, a pressure of 16,400 psig will cause a given volume of water to decrease by only 5% from its volume at atmospheric pressure.