  By means of interferometic 21-cm observations and a 3D kinematic modeling
technique, we study the gas kinematics of six HI-rich ultra-diffuse galaxies
(UDGs). We derive robust circular velocities and baryonic masses, that allow us
to study the position of our UDGs with respect to the baryonic Tully-Fisher
relation (BTFR). Somewhat surprisingly, we find that these galaxies are strong
outliers from the BTFR, rotating too slowly for their baryonic mass. Moreover,
their position in the circular velocity--baryonic mass plane implies that they
have a baryon fraction inside their virial radii compatible with the
cosmological mean, meaning that they have no "missing baryons". Unexpectedly,
the dynamics of our galaxies are dominated by the baryons, leaving small room
for dark matter inside their discs.
