Factors such as the contour of the seabed and geography of the shoreline have a major affect on the height and timing of tides. In simplistic terms it's similar to how waves behave e.g. summing and subtraction and increased height in shallow water. I do recall reading that the tide is essentially a wave that circles the Earth at 800 km/ph so this if no surprise.
Gord May "If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
We had an interesting experience at the northern tip of Queensland where getting the tides and currents right really matters. Between three boats we had four different electronic tide/current predictors (Garmin, Navionics, etc) along with printed tables from the Queenslandgovernment and they were different by hours. The most accurate was the printed book.