The ocean appears blue primarily because water itself absorbs colors in the red part of the light spectrum and reflects and scatters the blue part. Sunlight contains all colors, but the longer wavelengths like red, orange, and yellow are absorbed quickly by water, while the shorter wavelengths like blue and violet penetrate deeper and are scattered, making the ocean look blue to our eyes. This effect remains even below the surface, so it is not just a reflection of the sky, though the sky's color can influence the ocean's appearance at the surface. Other factors like depth, particles, and organisms such as phytoplankton can alter the ocean's color in some areas, causing green, brown, or other hues.
Key reasons for ocean blue color:
- Water absorbs longer wavelengths (red, orange) more strongly.
- Blue light penetrates deeper and is scattered by water molecules and tiny particles.
- The effect is intrinsic to water and not only due to sky reflection.
- Depth and clarity affect the shade of blue.
- Presence of sediments, phytoplankton, or other materials can change color locally.
This explains why the ocean generally looks blue to us.
