  The goal of my lecture is to present the introduction into the hydrodynamical
version of the Grad-Shafranov equation. Although not so well-known as the full
MHD one, it allows us to clarify the nontrivial structure of the Grad-Shafranov
approach as well as to discuss the simplest version of the 3+1-split language
-- the most convenient one for the description of the ideal flows in the
vicinity of a rotating black hole.
