The official vignette provides a good starting point. To get it, install gsw and then type vignette("gsw") in an R console.

Below is a list of functions provided by gsw. The links under the function names connect to the relevant TEOS-10 documentation. Note that the function names match those used in the Matlab version, and that the arguments also match except that longitude and latitude are used instead of abbreviations.

This website is written in Jekyll, and the source is available on GitHub.