  The formation of dispersive shock waves in the one-dimensional Bose gas
represents a limitation of Generalized Hydrodynamics (GHD) due to the
coarse-grained nature of the theory. Nevertheless, GHD accurately captures the
long wavelength behavior indicating an implicit knowledge of the underlying
microscopic physics. Such representation are already known through the Whitham
modulation theory, where dispersion-less equations describe the evolution of
the slowly varying shock wave parameters. Here we study the correspondence
between Whithams approach to the Gross-Pitaevskii equation and GHD in the
semi-classical limit. Our findings enable the recovery of the shock wave
solution directly from GHD simulations, which we demonstrate for both zero and
finite temperature. Additionally, we study how free expansion protocols affect
the shock wave density and their implications for experimental detection. The
combined picture of Whitham and GHD lends itself to additional physical
interpretation regarding the formation of shock waves. Further, this picture
exhibits clear analogies to the theory of Quantum GHD, and we discuss possible
routes to establish an explicit connection between them.
