The OceanParcels project develops Parcels (Probably A Really Computationally Efficient Lagrangian Simulator), a set of Python classes and methods to create customisable particle tracking simulations using output from Ocean Circulation models. Parcels can be used to track passive and active particulates such as water, plankton, plastic and fish. The code from the OceanParcels project is licensed under an open source MIT license and can be downloaded from github.com/OceanParcels/parcels or installed via anaconda.org/conda-forge/parcels.