Tides

The gravitational pull of the Moon causes two bulges of water on Earth: one directly under the Moon and another on the opposite side. The Earth rotates beneath these bulges, causing high tides when a bulge is present and low tides when it's not.

While it seems logical to have two high and two low tides daily, this isn't always the case. The shape of the seabed and the Earth's rotation, which causes large ocean whirlpools, significantly influence tidal patterns. For example, the difference between high and low tide can be massive in narrow passages like between Folkestone and Dover.

There are three main tidal patterns: semi-diurnal (two equal high and low tides daily), diurnal (one high and one low tide daily), and mixed (two unequal high and low tides daily).

The Sun also creates two bulges of water, though smaller due to its greater distance. During full and new moons, the Sun and Moon's gravitational pulls align, resulting in extra high high tides and extra low low tides, known as spring tides.

When the Sun and Moon are at 90-degree angles (during quarter moons), their gravitational forces work against each other, leading to the smallest tides, called neap tides. A large difference between high and low tide results in strong currents, which can be important for activities like diving.