Fig. 2. The wake behind a steadily swimming eel. The short black arrows indicate the flow velocity. The meandering grey arrow indicates the path of the tail tip and the swimming direction. All eels are swimming from right to left and have just left the field of view. The colour tiles indicate the level of vorticity in the flow, blue for clockwise vorticity, red for counterclockwise vorticity. Darker shades indicate higher levels of vorticity. The field of view is 108 mmx108 mm. (A) Eel (body length L=0.08 m) swimming at speed U=0.12 m s^-1. Sequence 1, see Table 1. Tail and body vortices have moved away from their initial shedding position (filled and open circles, respectively) close to the tail path (grey line). The shed vortices are visible in the flow field as areas of elevated vorticity. (B) Eel (L=0.10 m) swimming at U=0.14 m s^-1. Sequence 2, see Table 1. (C) Eel (L=0.10 m) swimming at U=0.12 m s^-1. Sequence 3, see Table 1.