XTide is a package that provides tide and current predictions in a wide variety of formats. Graphs, text listings, and calendars can be generated, or a tide clock can be provided on your desktop.
XTide can work with the X window system, plain text terminals, or the web. This is accomplished with three separate programs: the interactive interface (xtide), the non-interactive or command line interface (tide), and the web interface (xttpd).
The algorithm that XTide uses to predict tides is used by the National Ocean Service in the U.S. It is significantly more accurate than the simple tide clocks that can be bought in novelty stores. However, it takes more to predict tides accurately than just a spiffy algorithm -- data are required for every tidal prediction location. This package provides a sample data set for only one location so you can try out the package, but anything useful requires the data packaged in the xtide-data package (or downloaded from the XTide ftp site).