pos[{x_,z_},t_]:={x,z}+h Exp[k z]Cos[t]{-Sin[k x],Cos[k x]}

pos[{x_,z_},t_]:={x,z}+h Exp[k z]{-Sin[k x-t],Cos[k x-t]}

wl=80;
k=2Pi/wl;
center=Flatten[Table[{i,j},{i,-wl,wl,5},{j,-wl/2,0,5}],1];

h=5.;

movie=Table[Graphics[{FaceForm[Blue],Map[Disk[pos[#,t]]&,center]},ImageSize->700,PlotRange->{{-wl-2h,wl+2h},{-wl/2-2h,2h}}],{t,0,2Pi,2Pi/50}];

ListAnimate[movie]