Tides
NOAA Center for Operational Oceanographic Products and Services
The National Ocean and Atmosphere Administration--a unit of the US Department of Commerce--looks after tide observations and predictions.. Tide predictions are based on calculations of the relative position of the sun, the moon, and the earth; and on historic observations of sea level at the point of interest.
While the predictions are pretty good, they do not include predictions of the wind, barometric pressure, and long ocean waves such as seismic sea waves or tsunami. A comparison of the observed and predicted tide heights reveals the combined effect of these other factors. In this area they have been small historically. In areas subject to tropical storms, or shallow water areas subject to seismic sea waves, these effects can be many times the predicted tide heights.