The Global Ocean Health Index measures performance of ten societal goals for healthy oceans on a quantitative scale of increasing health from 0 to 100, and combines these scores into a single Index score, for each country and globally. The Global Ocean Health Index involves synthesizing highly heterogeneous information from nearly one hundred sources. Data from each source are formatted and used to calculate Index scores using freely available coding and version control software. One of the goals of the project is to make all their data and methods available to anyone who wants to further explore the results or use the data for other projects.