  We present results of a large, high resolution 3D hydrodynamical simulation
of the surface layers of a DA white dwarf (WD) with $T_{\rm eff}=11800$ K and
$\log(g)=8$ using the ANTARES code, the widest and deepest such simulation to
date. Our simulations are in good agreement with previous calculations in the
Schwarzschild-unstable region and in the overshooting region immediately
beneath it. Farther below, in the wave-dominated region, we find that the rms
horizontal velocities decay with depth more rapidly than the vertical ones.
Since mixing requires both vertical and horizontal displacements, this could
have consequences for the size of the region that is well mixed by convection,
if this trend is found to hold for deeper layers. We discuss how the size of
the mixed region affects the calculated settling times and inferred
steady-state accretion rates for WDs with metals observed in their atmospheres.
