A glass of water looks clear, but when we look out at the ocean, it appears blue. There are two reasons that the human eye to see the ocean as blue. The first relates to how humans see light waves coming from the sun. The second reason depends on how far a glass of water appear away a person is from a water For example, turquoise blue But th source. clear, yet shallow tropical water in the tropics looks deep ocean looks dark marine blue from far away.