From: The World In Your Head by Steven Lehar

Fig. 8.2 Various patterns of standing waves on fluid surfaces generated by vibrating the containing vessels with various driving frequencies, producing (A) hexagonal, (B) rectangular lattice, and (C) quasi-crystal patterns, among many more. (D) This pattern is defined more by the shape of the walls of the container than by the driving waveform, showing how interference patterns in the resonating system tend to subdivide the resonating system into periodic and symmetric subpatterns in an essentially Gestalt manner.