High and low tides

Highest and lowest tides every year occur when the sun and Moon are aligned. This is because the gravitational effects of the Moon and sun are additive. It's easy to see that when the sun lines up with the Moon and the Earth, as during a New Moon or Full Moon, a configuration also called "syzygy," the tidal effect is increased. These are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal.

On the other hand, if the sun and the Moon are 90 degrees apart in relation to an observer on Earth as during the half Moon phases known as First Quarter Moon or Third Quarter Moon. During these times, tides not as high as they normally would be. This is because despite its greater distance, the sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the Moon's pull. This phenomenon of lower high tides is called a neap tide.

The height of the tides can also vary during the course of a month because the Moon is not always the same distance from the Earth. At the perigee, or closest distance the Moon’s orbit will bring it to Earth, its gravitational forces can increase by almost 50%, and this stronger force leads to high tides. Likewise, when the Moon is farther away from the Earth and reaches the apogee, the tides are mild.

When the body of water is great enough, like an ocean, incredible tidal effects can occur. The bay of Fundry in Nova Scotia Canada has reported the greatest tidal shifts on the planet, with over 53 feet difference in height between low and high tides!