  In the geometry of the circular hydraulic jump, the velocity of the liquid in
the interior region exceeds the speed of capillary-gravity waves (ripplons),
whose spectrum is `relativistic' in the shallow water limit. The velocity flow
is radial and outward, and thus the relativistic ripplons cannot propagating
into the interior region. In terms of the effective 2+1 dimensional
Painleve-Gullstrand metric appropriate for the propagating ripplons, the
interior region imitates the white hole. The hydraulic jump represents the
physical singularity at the white-hole horizon. The instability of the vacuum
in the ergoregion inside the circular hydraulic jump and its observation in
recent experiments on superfluid 4He by E. Rolley, C. Guthmann, M.S. Pettersen
and C. Chevallier in physics/0508200 are discussed.
