The ocean: what could be more beautiful than watching the waves? When the water level surprised your tanning session and drowned your towel, you probably wondered why the tide rises and falls! In this article, we explain the phenomenon of tides. What is a tide? Let's start by answering a basic question: what is the tide? Before delving into further depth on the genesis of the tide (avoiding overly scientific explanations), let's answer a simple question: what is the tide? It is a regular movement of the level of the sea and the oceans. This phenomenon causes either a rise or a fall of the water. The big question is how the tides are formed! The phenomenon of tides is not simple, it is due to several factors: mainly to the attraction of the Moon and the Sun on the Earth. The tide is strongly influenced by the gravitational force of the Moon (because of its proximity to the Earth). Its attraction on our planet, attracts water to it. As for the Sun, it attracts the surface of the water in the same way, but in a smaller proportion than the Moon (due to its distance). These two stars are not the only ones to impact the level of the sea and oceans. Our lovely planet Earth also plays a role in the tidal phenomenon. When you take a turn, your car is attracted to the outside of the road, it's the same principle for the water surface! The surface of the water moves away from the center of the earth, a phenomenon caused by the earth itself when it rotates: this is the centrifugal force. But what happens when the tide is high? A basic explanation is that when the sea or ocean is closer to the Moon, the tide rises. (water is strongly attracted). The tide will be low when the surface of the water is no longer facing the Moon, nor attracted by the centrifugal force. Let us specify that other factors have an impact on the tides: the size of the water surface, the weather... Why two tides per day? You don't know when the tide will be high or low? For you, it is a real headache to plan a walk on the beach or a swim during your favorite tide? Now that you understand how the tides work, let's talk about the tidal cycle. Theoretically, there are two low tides and two high tides per day (rotation of the Earth). This type of tide is called "semi-diurnal". That is to say that the level of the two high tides is almost equal, ditto for the two low tides. This phenomenon is particularly observed in the Atlantic Ocean. All oceans have a tidal cycle. However, there are different types of tides across the planet. Globally, the tides are of the semi-diurnal type (mentioned earlier), and of the semi-diurnal type with diurnal inequality. This scientific expression means that there are two high and low tides but they can be very different from each other. This is particularly the case on the west coast of the United States. There are so-called "diurnal" tides, which mean a single high and low tide in 24 hours, as well as so-called "mixed" tides (diurnal and semi-diurnal tides). But these last two only concern a few seas in the world. To know the type of tides near you, take a look at the site of the hydrographic and oceanographic service of the Navy.