  We investigate the circumstellar dust shell of the water fountain source IRAS
16342-3814. We performed two-dimensional radiative transfer modeling of the
dust shell, taking into account previously observed spectral energy
distributions (SEDs) and our new $J$-band imaging and $H$- and $K_S$-band
imaging polarimetry obtained using the VLT/NACO instrument. Previous
observations expect an optically thick torus in the equatorial plane because of
a striking bipolar appearance and a large viewing angle of 30 - 40$\degr$.
However, models with such a torus as well as a bipolar lobe and an AGB shell
cannot fit the SED and the images simultaneously. We find that an additional
optically and geometrically thick disk located inside a massive torus solves
this problem. The masses of the disk and the torus are estimated to be 0.01
$M_{\sun}$ at the $a_\mathrm{max}=100 \mu$m dust and 1 $M_{\sun}$ at
$a_\mathrm{max}=10 \mu$m dust, respectively. We discuss a possible formation
scenario for the disk and torus based on a similar mechanism to the equatorial
back flow. IRAS 16342-3814 is expected to undergo mass loss at a high rate. The
radiation from the central star is shielded by the dust that was ejected in the
subsequent mass loss event. As a result, the radiation pressure on dust
particles cannot govern the motion of the particles anymore. The mass loss flow
can be concentrated in the equatorial plane by help of an interaction, which
might be the gravitational attraction by the companion, if it exists in IRAS
16342-3814. A fraction of the ejecta is captured in a circum-companion or
circum-binary disk and the remains are escaping from the central star(s) and
form the massive torus.
