Figure 3. Illustration of procedure employed to define angular parameters studied. The angle of flexion at the foot in relation to the shin (Knee-Ankle-Tail) (A). Angle of bend in the proximal part of the fin in relation to the foot (Ankle-Tail-Middle) (B). Angles of attack were estimated according the generally accepted definition. Between the lines connecting the points marked on the respectively parts of its surface and the lines determining the direction of swimming (parallel to the water surface) - Angle of attack of distal part of monofin (Middle-Edge- Horizontal) (C) even as angle of attack of its entire surface (Tail-Edge-Horizontal) (D) (adapted from Rejman and Ochmann, 2009).