Why the Moon Causes Tides

The important part is the difference in gravity

The Moon attracts all of Earth, but its pull is stronger on the near side and weaker on the far side than at Earth's center. These differences stretch the Earth-ocean system. A simplified ocean-covered Earth develops two tidal bulges, rather than just one pile of water directly under the Moon.

The far-side bulge does not mean the Moon repels water. Gravity remains attractive. The diagram describes motion relative to Earth's center; it is a starting model for the driving force, not a literal timetable for every coast.

Reference: NOAA: Gravity and Tidal Bulges

Spring and neap tides describe a range

The Sun also raises tides. Near new and full Moon, the Sun-Moon geometry tends to reinforce the tidal range, producing spring tides. Near first and third quarter, the combined effect generally produces the smaller ranges called neap tides. Spring refers to the water's springing forth, not the season.

Range means the difference between high and low water. In an invented table with high water at 2.4 meters and low water at 0.6 meters relative to the same reference, the range is 1.8 meters. Those heights do not describe wave height or the depth at every nearby beach.

Reference: NOAA: Spring and Neap Tides

A real coast needs a local prediction

Continents, basin depth, friction, and coastline shape change the ocean's response. High tide does not generally occur exactly when the Moon is overhead. Some locations have two similar high tides per day, others unequal pairs, and others mainly a once-daily pattern.

That is why Moon phase, Moonrise, and Moonset are not substitutes for an official local tide table. Wind, air pressure, waves, and tidal currents add further complications. A small neap range is not a declaration that coastal conditions are safe.

Reference: NOAA: The Moon and High Tide

Compare a few weeks of predictions

For a learning exercise, mark lunar phases beside several weeks of predictions from one official tide station. Look for the broad range pattern and any lag, rather than forcing every peak to match the exact phase time.

• Keep the station, date, time zone, units, and reference level with the figures.
• Distinguish predicted levels from measured observations and from current-speed forecasts.
• Use local official conditions and warnings for coastal decisions, not this general astronomy explanation.