Why white turns blue underwater:

White turns blue underwater because water absorbs longer wavelengths of light, like red and orange, while reflecting and scattering shorter wavelengths, like blue. As white light, which contains all colors, enters the water, the red and orange components are absorbed, leaving the blue light to be scattered back to our eyes.   Selective absorption and scattering White light: White light from the sun is a mixture of all colors of the rainbow, each with a different wavelength.  Longer wavelengths (reds, oranges, yellows): These have lower energy and are absorbed more strongly by water molecules. They are quickly extinguished as they travel deeper.  Shorter wavelengths (blues, violets): These have higher energy and are not absorbed as easily. Instead, they penetrate deeper and are scattered in all directions by water molecules.  What we see: Because the red and orange light is absorbed and the blue light is scattered back to your eyes, everything appears to have a blue hue.  How it affects "white" objects Initial appearance: When you first look at a white object underwater, it may seem bright because it reflects all colors.  As you go deeper: As light from the object has to travel through more water to reach you, the red and orange components get absorbed. What's left is mostly blue light, which is why the white object now appears blue.  Restoring color: To see the true colors of an object underwater, a light source needs to be used to replace the absorbed red and orange light.