I have the topo (Entire US) software for a garmin emap. I'm relatively happy with this because it has both land navagation and marine. It does not have the tides which would be nice. The problem I have is that the unit I have only has a 8 mg chip and you can't download much of the data ( a few counties). You can get a bigger chip, but there very expensive. I gues Garmin has a new version called WAAS 76 that is waterproof and has the tides built in. These units change fast with more stuff for the $$.