  The generalized Zermelo navigation problem looks for the shortest time paths
in an environment, modeled by a Finsler manifold (M,F), under the influence of
wind or current, represented by a vector field W. The main objective of this
paper is to investigate the relationship between the isoparametric functions on
the manifold M with and without the presence of the vector field W. For the
positive-definite cases, we also compare the mean curvatures in the manifold.
Overall, we follow a coordinate-free approach.
