We know that a real vacuum doesn't exist. By describing it as a superfluid quantum space (SQS) it's shown how gravity can arise as absorption of space's quanta effected by fermions, when they are described as topological defects of SQS (superfluid vortices similar to those observed in superfluid helium-4 nanodroplets). By applying this hypothesis, Newton's law of universal gravitation has been obtained through CFD simulations. In this case, a gravitational field is an incoming flow of space's quanta, mathematically analogous to the virtual flow described in Gauss's law for gravity, and this leads to the formulation of a fluid equivalence principle, able to show how gravity is the origin of all relativistic effects, also in special relativity, producing a considerable simplification in the theory of relativity. It is shown how the fluid dynamics of a SQS is able to describe curved space and gravitational waves. Not less important when discussing fluid space, this hypothesis would not conflict with the MM-experiment and would open a new scenario on the nature of light and Hubble's law. A simple experiment is suggested to verify fluid quantum gravity and relativity on the ISS.