The color of water can seem very different depending on distance , too. A bathtub or glass full of water always looks clears, letting you see your reflection. this is because it is being viewed over a short distance. Actually, a glass of water is slightly blue. In fact, if the volume of water was sufficiently large ,it would appear blue. depending on the water source, the color of water is not always the same> In deep water, the water looks dark blue or bluish-green because deep water only transmits a small amount of blue light. The deeper the water, the darker blue the ocean seems. Another factor that makes the ocean appear dark blue is the oxygen in the water. Sunlight is often scattered by the oxygen in the water, making it harder to reflect the blue light.