NOAA
Noaa: National Ocean Service: Education: Tides and Water Levels
A great resource for explaining and understanding tides. Find out what tides are and why it is so important to monitor them. This is an extensive tutorial followed by a set of review questions. All of the information can be downloaded as...
CK-12 Foundation
Ck 12: Earth Science: Tides
[Free Registration/Login may be required to access all resource tools.] Reveals tidal patterns and that tides are caused by the gravitational attraction of the Sun and Moon to Earth.