Fig. 4.

Examples of time series of the tail tip amplitude for one given individual (fish 2) within the school and its two nearest neighbors (fish 1 and 3). (A and B) Low (A) and high (B) swimming speed. The in-phase (IP) and out-of-phase (OP) swimming regimes are also shown. (C and D) Evolution of the phase difference $\mathrm{{\rm Y}}$ between fish 2 and its two nearest neighbors (fish 1 and 3) showing a nonsynchronized state ($NS$) at low swimming speed (C) and strongly synchronized state ($S$) at high swimming speeds (D). D, Insets show zooms in the case of synchronized swimming that are either around $0$ (for IP synchronization) or $\pi$ (for OP synchronization).