White arrows show the direction

White arrows show the direction of wave propagation, red arrows show the direction of the
surface flow and the ball motion.
a, Wave field produced by the cylindrical wave maker at lower acceleration shows nearly planar
waves propagating away from the wave maker (seen at the bottom of the panel). b, These
waves produce strong outward jet in the direction of the wave propagation and the return
flows towards the edges of the cylinder. c, As the wave maker acceleration is increased (by 30%
in comparison with a) the modulation instability destroys the wave planarity generating 3D
wave field shown here. d, This 3D wave field generates strong inward directed jet towards the
center of the cylinder and the outward return flows away from the edges of the cylinder. e,
Consecutive positions of the ping-pong ball (2.7 g, 40 mm diameter) placed on the water
surface perturbed by a linear wave (as in a). Time interval between frames is 0.87 s. f, Motion
of the ping-pong ball in the inward jet (c,d). Time interval between frames is 3.3 s