  We use ultra-high-speed video imaging to look at the initial contact of a
drop impacting onto a liquid layer. We observe experimentally the vortex street
and the bubble-ring entrapments predicted numerically, for high impact
velocities, by Thoraval et al. [Phys. Rev. Lett. 108, 264506 (2012)]. These
dynamics occur mostly within 50 {\mu}s after the first contact, requiring
imaging at 1 million frames/sec. For a water drop impacting onto a thin layer
of water, the entrapment of isolated bubbles starts through azimuthal
instability, which forms at low impact velocities, in the neck connecting the
drop and pool. For Re above about 12 000, up to 10 partial bubble-rings have
been observed at the base of the ejecta, starting when the contact is about 20%
of the drop size. More regular bubble rings are observed for a pool of ethanol
or methanol. The video imaging shows rotation around some of these air
cylinders, which can temporarily delay their breakup into microbubbles. The
different refractive index in the pool liquid reveals the destabilization of
the vortices and the formation of streamwise vortices and intricate vortex
tangles. Fine-scale axisymmetry is thereby destroyed. We show also that the
shape of the drop has a strong influence on these dynamics.
