On a SPOT-4 panchromatic image of the Mid-Atlantic Bight, a zipper-like pattern is observed due to the nonlinear internal wave-wave interaction process. The pre-interaction and post-interaction angles are measured approximately and, respectively. The length of merged fronts in the interaction zone decreases from front to rear. It indicates a fundamentally unsteady interaction. The brightness of the post-interaction waves is much weaker than the pre-interaction waves, which implies much smaller wave amplitudes. The brightness of merged fronts is much stronger, which implies larger wave amplitudes. These characteristics qualitatively agree well with numerical results of Mach interaction of large amplitude waves by Tanaka . The exceptionally large amplitudes in the interaction zone may pose threats to underwater structures.