We discuss the propagation of nonlinear electromagnetic short waves in a magnetically saturated ferromagnetic thick film. The sample is magnetized to saturation by a field perpendicular to both the film plane and the propagation direction. A (2+1) dimensional asymptotic model equation generalizing the sine-Gordon one is derived. Line soliton solutions are exhibited; their stability condition is derived. When unstable, line solitons decay into stable two-dimensional lumps, which are studied both numerically and analytically.