The researchers studied the dynamics of a liquid jet injected into a vertically flowing soap film. As the speed of the flowing soap film increased, they observed a transition in the jet from straight to wavy, with waves propagating downstream. At higher film speeds, secondary branching structures formed at the wave crests, and more complex patterns emerged. The straight-to-wavy transition differs from the Rayleigh instability that causes drop formation via surface tension. However, similar "snake modes" have been seen in a liquid jet within a gaseous jet. The wavy jet also resembles elastic structures in soap films, showing an analogy between viscous jet and elastic structure dynamics.