The global ocean is divided into several zones, from national to international waters. At the national level, governments can easily create these marine protected areas. The legal framework is much more complex when dealing with international waters.
The Protected Planet website presents official coverage statistics for marine protected areas. Information are updated monthly with contributions from governments, non-governmental organizations and landowners. The project is managed by the United Nations World Conservation Monitoring Centre for the Environment (UNEP-WCMC) with the support of IUCN and its World Commission on Protected Areas (WCPA).
As for 2019, the website covers 15,059 marine protected areas covering an area of more than 27 million km2, or 7.68% of the oceans. The data is available in .pdf, .shp and .csv formats.