WHY is the sea blue and the water in the glass clear?

 Yes, it is true that clear water appears blue, although the shade of blue is often so faint that it is not noticeable in small containers. This is because water absorbs colors from the blue part of the visible light spectrum, and when light passes through a large volume of water, it scatters in all directions, making the water appear blue. Additionally, the color of water can also be influenced by its surroundings. For example, if the water is in a reservoir or other body of water that is surrounded by blue sky, it may take on a bluish hue due to the reflection of the sky's color.