the human eye sees the ocean as blus due to light waves coming from the sun and the distance a person is from a water source. When the sun shines on the ocean, only the green and blue spectrum of light get reflected back. This is why the ocean seems blue. The color of water can also seem very different depending on the distance you are from it. A bathtub or glass full of water always looks clear water, the ocean only transmits a small amount of blue light, so it looks dark blue.