  The first detailed VLA mapping of the neutral hydrogen distribution in the
isolated, edge-on spiral galaxy NGC 3044 is presented. Physical parameters
determined for this galaxy are typical for galaxies of its morphological class
(SBc). We have modelled the HI spectra in order to derive its global density
and velocity distributions. An HI scale height of 420 h^(-1) pc is thus found.
This can be compared to the 8 kpc radio continuum halo found previously.
  The present study reveals an asymmetry in the HI distribution as well as
numerous high-latitude HI structures at various galactocentric radii.
  Twelve high-latitude features were catalogued, of which four exhibit the
signature of an expanding shell. There is some correlation of these features
with features observed in the radio continuum from independent data. The most
massive shell (Feature 10) extends out to 6h^(-1) kpc above the galactic disk.
The radii and masses of these shells range from 1.2h^(-1) - 2.0h^(-1) kpc and
1.6 10^7 - 5.5 10^7h^(-2) solar masses, respectively. We have investigated the
possibility that the supershells could have been produced by external impacting
clouds, but conclude that this scenario is unattractive, given the age of the
shells, the isolation of the galaxy, and the lack of any observed features
sufficiently massive to form the shells in the vicinity of the galaxy.
Therefore, an internal origin is suggested. Since the implied input energies
from supernovae are extremely high (e.g. from 1.4 10^(53)h^(-20 - 7.4
10^(55)h^(-2) ergs, corresponding to 400 - 74,000 supernovae), we suggest that
some additional energy (e.g. from magnetic fields) may be needed to produce the
observed supershells.
