  We study the statistics of free-surface turbulence at large Reynolds numbers
produced by direct numerical simulations in a fluid layer at different
thickness with fixed characteristic forcing scale. We observe the production of
a transient inverse cascade, with a duration which depends on the thickness of
the layer, followed by a transition to three-dimensional turbulence initially
produced close to the bottom, no-slip boundary. By switching off the forcing,
we study the decaying turbulent regime and we find that it cannot be described
by an exponential law. Our results show that boundary conditions play a
fundamental role in the nature of turbulence produced in thin layers and give
limits on the conditions to produce a two-dimensional phenomenology.
