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