  A bouncing droplet, self-propelled by its interaction with the waves it
generates, forms a classical wave-particle association called a "walker."
Previous works have demonstrated that the dynamics of a single walker is driven
by its global surface wave field that retains information on its past
trajectory. Here, we investigate the energy stored in this wave field for two
coupled walkers and how it conveys an interaction between them. For this
purpose, we characterize experimentally the "promenade modes" where two walkers
are bound, and propagate together. Their possible binding distances take
discrete values, and the velocity of the pair depends on their mutual binding.
The mean parallel motion can be either rectilinear or oscillating. The
experimental results are recovered analytically with a simple theoretical
framework. A relation between the kinetic energy of the droplets and the total
energy of the standing waves is established.
