  The ratio between the shear viscosity and the entropy $\eta/s$ is considered
a universal measure of the strength of interactions in quantum systems. This
quantity was conjectured to have a universal lower bound $(1/4\pi)\hbar/k_{B}$,
which indicates a very strongly correlated quantum fluid. By solving the
quantum kinetic theory for a nodal-line semimetal in the hydrodynamic regime,
we show that $\eta/s\propto T$ violates the universal lower bound, scaling
towards zero with decreasing temperature $T$ in the perturbative limit. We find
that the hydrodynamic scattering time between collisions is nearly temperature
independent, up to logarithmic scaling corrections, and can be extremely short
for large nodal lines, near the Mott-Ragel-Ioffe limit. Our finding suggests
that nodal-line semimetals can be very strongly correlated quantum systems.
