In the Mediterranean Sea there are hardly any variations in sea level, unlike on the Atlantic coasts, where the tidal range (bathymetric difference between one high tide and the following low tide) can exceed four meters. Tides are the result of the gravitational attraction of the Moon and the Sun on large bodies of water. These forces of attraction generate standing waves of great length that move, covering and uncovering parts of the seabed.
| It seems incredible that the entire sandy surface of the Camariñas estuary, in Galicia, is completely submerged at high tide. And the opposite at low tide. The landscapes on the tidal coasts are constantly changing. © El Playólogo/Maremecum
The most curious thing is that the coastal morphology can increase or, on the contrary, decrease the effects of the tide, so when these waves move and meet narrow seas, gulfs and estuaries, a funnel effect is produced and with it the increase of the tidal amplitude, while in closed seas such as the Mediterranean, connected to the Atlantic Ocean by the Strait of Gibraltar, the effects of these waves are hardly perceived. The Mediterranean Sea does not have enough volume/surface area for the gravitational pull of the Moon and the Sun to be felt. The same is true for the lakes, which do not suffer from the tides.
| San Simon Island at high tide, when the passage between the island and the land is navigable. If you look closely, you can already see the sand tongue at the bottom of the image. © El Playólogo/Maremecum
The lack of knowledge of the tides by the Phoenician, Greek and Roman navigators was the reason why Caesar's armada was devastated off the coast of England when it ran aground during low tide. I have a lot to tell you about it, as I have been through that experience on several occasions (read below and I will tell you one of my anecdotes).
| Rodas Beach, Galicia. © El Playólogo/Maremecum
And now let me tell you about one of the occasions whenthe tides played a dirty trick on me. If you look closely at this photograph of Rodas beach, in the Cies Islands, Galicia, you can see my boat anchored in front of the beach at high tide. Well, I remember arriving sailing in the middle of the afternoon and seeing on the depth sounder that there was more than 3 m of draft, so I left the boat anchored and went ashore with a small auxiliary. I spent the afternoon photographing the island and enjoying the excursion until nightfall when I returned to the beach. And what a surprise! I had the boat stranded on the sand, totally dry! So I had to sit on the beach and wait for the tide to come back in so I could sail out. It became totally dark and I had to go back totally blind, as I had no charts and at that time I didn't use any electronic device, plotter or GPS to locate myself. That's how I set course for the island of San Simon, at the bottom of the Vigo estuary, in front of which I had my motorhome parked waiting patiently for me (I was starving and sleepy!). Well, I had the fabulous idea of passing between the island and the land, at night, and with the tide still very low. And it is true that the depth sounder said that there was two meters of water, but suddenly I got stuck, stranded on the sandy tongue between the island and the land, although just before the depth sounder marked more than 2 m of water! That's why I've always said that the depth sounder is good for getting an idea, but it doesn't show you the shallows or the sand bars that suddenly appear where you don't expect them. I had to take off my pants, get in the water and push the boat. The water temperature (I do remember this well) was 14 degrees, so I returned to the motorhome with my genitals in a state of hibernation....
| This is San Simon Island at mid-tide, when I was stranded. © El Playólogo/Maremecum
And speaking of stories, I still remember the story of Toni, that fisherman from the island who during an IMSERSO trip to the Galician estuaries discovered for the first time the meaning of the tides. The good man had acquired a small bottle filled with sea water, a few shells and a handful of sand that was sold to him as a souvenir on the island of La Toja. In the afternoon he approached the shore and, astonished, discovered the passing drought. And the magnitude of the business! He looked at his hands and cried out to heaven: all my life working at sea and it had never occurred to me!