The data
Everything the map draws, in three formats.
What you may do with it
The facts — names, coordinates, countries, shore types, Wikipedia links — come from Wikidata and are CC0. The sea temperatures come from NOAA OISST v2.1 and are a work of the US government, in the public domain. Both are yours to use.
The photographs are not in these files and are not ours to license. They live on Wikimedia Commons under their own terms; the files carry the file name, the photographer and the licence so you can honour them.
What this is not
It is not a complete register of the world's beaches, and it is not a survey. It is the subset of Wikidata that could be mapped honestly, with a temperature attached where NOAA's grid could speak for the shore. How it is chosen sets out every rule.