  We discuss the production of multiple astrophysical messengers (neutrinos,
cosmic rays, gamma-rays) in the Gamma-Ray Burst (GRB) internal shock scenario,
focusing on the impact of the collision dynamics between two shells on the
fireball evolution. In addition to the inelastic case, in which plasma shells
merge when they collide, we study the Ultra Efficient Shock scenario, in which
a fraction of the internal energy is re-converted into kinetic energy and,
consequently, the two shells survive and remain in the system. We find that in
all cases a quasi-diffuse neutrino flux from GRBs at the level of $10^{-11}$ to
$10^{-10} \, \mathrm{GeV \, cm^{-2} \, s^{-1} \, sr^{-1}}$ (per flavor) is
expected for protons and a baryonic loading of ten, which is potentially within
the reach of IceCube-Gen2. The highest impact of the collision model for
multi-messenger production is observed for the Ultra Efficient Shock scenario,
that promises high conversion efficiencies from kinetic to radiated energy.
However, the assumption that the plasma shells separate after a collision and
survive as separate shells within the fireball is found to be justified too
rarely in a multi-collision model that uses hydrodynamical simulations with the
PLUTO code for individual shell collisions.
