Jullouville beach and the turquoise waters of the seaJullouville beach and the turquoise waters of the sea
©Jullouville Beach|Estelle Cohier
Blue, green, turquoise waters...Why does the sea change color?

Why is the sea sometimes green and blue in places?

A story of light...

Depending on the season, the weather and where you are in Destination Granville Terre et Mer, you’ll have the chance to see the sea change color. Sometimes gray, sometimes dark blue, sometimes light blue, green or turquoise, the sea puts on a magnificent show! But why does the sea change color? How can we explain this sublime camaïeu de bleu?

A landscape of


Great sunshine, fine sand, transparent then turquoise water in places, that’s the dreamy postcard we sometimes – quite often, in fact – experience on Destination Granville Terre et Mer. Some people think that the color of the sea is a reflection of the blue sky, but all you have to do is take a little water in your hand to realize that it really is transparent.

Then the explanation doesn’t come from the sky, or just a little…. It’s actually the light penetrating the water. The sun’s rays are not just white: they are a visible spectrum of colors. As they progress through the sea, these disappear. At first, the rays are yellow, then turn red, green and finally blue.

Light and


The hue we observe also depends on the depth of the sea. At the seaside, it’s not very important, which prevents the absorption of the sun’s rays, which is why, there’s so much transparency…. This transparency is actually very visible on the archipel de Chausey. The further offshore we go, the darker and darker the blue becomes.

Sometimes, the water turns green, due to the presence of phytoplankton which contains chlorophyll, and absorbs blue radiation, bringing out another, more “plant-like” hue. The algae present in the Channel Sea on our Destination Granville Terre et Mer also influence the green color of the sea.

50 shades of


“What we need to remember is that the sea puts out its blue coat in good weather, when the sky itself is blue, and that it puts out its gray coat in bad weather, when this is also gray. The variations in depth at sea give the different shades of color that we observe.”

Estelle, in love with the colors of Destination Granville Terre et Mer