  Highly collimated jets found in AGB and post-AGB stars are expected to play
an important role for shaping planetary nebulae. Recent VLBI observations of
H2O maser sources have revealed that some of the spatio-kinematical structures
of H2O maser sources exhibit stellar jets with extremely spatially and
kinematically high collimation. Such stellar H2O maser jets, so-called "water
fountain" sources, have been identified in about 10 sources to date. Here we
review recent VLBI observations and relevant observational results of the water
fountain sources. They have revealed a typical dynamical age and the detailed
kinematical structures of the water fountains, possibility of the existence of
"equatorial flows", and the evolutionary status of the host stars. The location
and kinematics of one of the water fountain sources in the Galaxy is also
revealed and shown here.
