  The standard model of cosmology suggests the existence of two components,
"dark matter" and "dark energy", which determine the fate of the Universe.
Their nature is still under investigation, and no direct proof of their
existences has emerged yet. There exist alternative models which reinterpret
the cosmological observations, for example by replacing the dark energy/dark
matter hypothesis by the existence of a unique dark component, the dark fluid,
which is able to mimic the behaviour of both components. After a quick review
of the cosmological constraints on this unifying dark fluid, we will present a
model of dark fluid based on a complex scalar field and discuss the problem of
the choice of the potential.
