To cite package ‘croc’ in publications use:

  Sumner M (2018). _croc: Tools for Ocean Colour_. R package version
  0.0.9, <https://github.com/sosoc/croc>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {croc: Tools for Ocean Colour},
    author = {Michael D. Sumner},
    year = {2018},
    note = {R package version 0.0.9},
    url = {https://github.com/sosoc/croc},
  }