Fairly accurate if one considers only sun, earth and moon position
There are THREE types of tides based on how the interaction of the sun & moon's gravitational effect do act on the tides - diurnal (once a day), semi-durnal (twice a day) and mixed (combinations of the two). Gravitational affects ...... versus *physical geography* are easy to predict mathematically so those 'benchmarks' of tidal datums are fairly accurate (but NOT including the local affects of 'wind tides' (surges) and flooding from rain, rivers, etc.) www.physicalgeography.net/fundamentals/8r.html