?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).
xtide is already packaged in the main Debian archive.
xtide homepage http://www.flaterco.com/xtide/
Short french presentation: http://www.tice.ac-versailles.fr/logicielslibres/spip.php?article76