"It is commonly believed that the sea is blue in colour is due to the sky reflecting on the surface of the water. The sea is still, however, blue. It remains blue, even when there are no skies above it. This has been confirmed through the experience of deep sea explorers. Generally speaking, every swimmer or diver throws himself in the midst of a blue environment, although being in the position of diving does not allow the diver to view the sky or his or her own image. In such a fashion, the author purposely pauses to explain the different viewpoints, clarifying the reasons behind the blueness of the sea. He commences with questions that may seem very simple on the surface. Is it true that the sea is blue? Is it just an optical illusion, resulting from the reflection of the sky, for instance? If the sea is truly blue, is this colour a part if its structure? Do particles dispersed in the water give the sea its blue colour? Does the water itself produce a blue colour? What if the sea only appears blue to us because it contains particles that have the same colour?
These are all questions that the author tries to answer. He also attempts to find convincing - even if temporary - explanations that may be reconsidered later, if needed."