  Ripplons -- gravity-capillary waves on the free surface of a liquid or at the
interfaces between two superfluids -- are the most favourable excitations for
simulation of the general-relativistic effects related to horizons and
ergoregions. The white-hole horizon for the ``relativistic'' ripplons at the
surface of the shallow liquid is easily simulated using the kitchen-bath
hydraulic jump. The same white-hole horizon is observed in quantum liquid --
superfluid 4He. The ergoregion for the ``non-relativistic'' ripplons is
generated in the experiments with two sliding 3He superfluids. The common
property experienced by all these ripplons is the Miles instability inside the
ergoregion or horizon. Because of the universality of the Miles instability,
one may expect that it could take place inside the horizon of the astrophysical
black holes, if there is a preferred reference frame which comes from the
trans-Planckian physics. If this is the case, the black hole would evapotate
much faster than due to the Hawking radiation. Hawking radiation from the
artificial black hole in terms of the quantum tunneling of phonons and ripplons
is also discussed.
