  We present a numerical study of the cubic-quintic nonlinear Schr\"odinger
equation in two transverse dimensions, relevant for the propagation of light in
certain exotic media. A well known feature of the model is the existence of
flat-top bright solitons of fixed intensity, whose dynamics resembles the
physics of a liquid. They support traveling wave solutions, consisting of
rarefaction pulses and vortex-antivortex pairs. In this work, we demonstrate
how the vortex-antivortex pairs can be generated in bright soliton collisions
displaying destructive interference followed by a snake instability. We then
discuss the collisional dynamics of the dark excitations for different initial
conditions. We describe a number of distinct phenomena including vortex
exchange modes, quasielastic flyby scattering, soliton-like crossing, fully
inelastic collisions and rarefaction pulse merging.
