  We explore the complex dynamics of a non-coalescing drop of moderate size
inside a circular hydraulic jump of the same liquid formed on a horizontal
disk. In this situation the drop is moving along the jump and one observes two
different motions: a periodic one (it orbitates at constant speed) and an
irregular one involving reversals of the orbital motion. Modeling the drop as a
rigid sphere exchanging friction with liquid across a thin film of air, we
recover the orbital motion and the internal rotation of the drop. This internal
rotation is experimentally observed.
