Muscle action is described by the notion of active distortions, emphasizing their kinematical role, the generation of movement.

Active distortions have been successfully used to model muscle in other contexts; here, this approach is used to implement a model for fish swimming.

Our model can be easily implemented in a Finite Elements Analysis, as distortions are available in most softwares.

Our simulations are easily reproducible by other scholars. This feature is very valuable, for modeling fish swimming.

Our results are in good agreements with the known ones