  The increase in moment of inertia of SF$_6$ in helium nanodroplets is
calculated using the quantum hydrodynamic approach. This required an extension
of the numerical solution to the hydrodynamic equation to three explicit
dimensions. Based upon an expansion of the density in terms of the lowest four
Octahedral spherical harmonics, the predicted increase in moment of inertia is
$170 {\rm u \AA^2}$, compared to an experimentally determined value of $310(10)
{\rm u \AA^2}$, i.e., 55% of the observed value. The difference is likely in at
least part due to lack of convergence with respect to the angular expansion,
but at present we do not have access to the full densities from which a higher
order expansion can be determined. The present results contradict those of Kwon
et al., J. Chem. Phys. {\bf 113}, 6469 (2000), who predicted that the
hydrodynamic theory predicted less than 10% of the observed increase in moment
of inertia.
