This page links to data from US states and territories Tide Stations to provide data regarding tides in that port. These links go to that stations homepage in turn and additional information can be viewed.
http://tidesandcurrents.noaa.gov/station_retrieve.shtml?type=Tide Data
This PDF document begins by setting the distinction between tides and tidal currents. It is a detailed lesson on tidal currents for the advanced learner. Good teacher site.
http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-09.pdf
Page is a lesson about tidal currents, provides glossary and links to other lessons. Does not include assessment questions.
http://www.lobstermanspage.net/tides/currents.html
Main page provides links to real time tide and current information and maps.
http://tidesonline.nos.noaa.gov/