  Observations of H$_2$O masers towards the post-AGB star and water fountain
source OH 009.1--0.4 were made as part of HOPS (The H$_2$O southern galactic
Plane Survey), with the Mopra radiotelescope. Together with followup
observations using the Australia Telescope Compact Array (ATCA), we have
identified H$_2$O maser emission over a velocity spread of nearly 400km/s
(--109 to +289km/s). This velocity spread appears to be the largest of any
known maser source in our Galaxy. High resolution observations with the ATCA
indicate the maser emission is confined to a region $0\farcs3 \times 0\farcs3$
and shows weak evidence for a separation of the red- and blueshifted maser
spots. We are unable to determine if the water fountain is projected along the
line of sight, or is inclined, but either way OH 009.1--0.4 is an interesting
source, worthy of followup observations.
