  We present a study of the distribution and kinematics of the neutral gas in
the low-inclination Scd galaxy NGC 6946. The galaxy has been observed for 192
hours at 21-cm with the Westerbork Synthesis Radio Telescope. These are among
the deepest observations ever obtained for a nearby galaxy. We detect
widespread high-velocity HI (up to about 100 km/s) and find 121 HI holes, most
of which are located in the inner regions where the gas density and the star
formation rate are higher. Much of the high-velocity gas appears to be related
to star formation and to be, in some cases, associated with HI holes. The
overall kinematics of the high-velocity gas is characterized by a slower
rotation as compared with the regular disk rotation. We conclude that the
high-velocity gas in NGC 6946 is extra-planar and has the same properties as
the gaseous halos observed in other spiral galaxies including the Milky Way.
Stellar feedback (galactic fountain) is probably at the origin of most of the
high-velocity gas and of the HI holes. There are also indications, especially
in the outer regions, -an extended HI plume, velocity anomalies, sharp edges,
and large-scale asymmmetries- pointing to tidal encounters and recent gas
accretion.
