Hello,
See also this discussion : FLOATS module status
FLOATS CPP key was no longer maintained and has been removed from the master branch for the next release.
Another tool with Lagrangian capabilities (parallelized with MPI) is available in the dev_2025_FOIL branch. An integration is planned for the next release.
And yes I also suggest Ichthyop using CROCO output, that could be a good offline way to do it.