To understand why the ocean water appears blue you must first understand why we see color the way we do. “When light hits an object – say a banana – the object absorbs some of the light and reflects the rest of it. Which wavelengths are rejected and absorbed depend on the properties of the object.” (Stephanie Pappas, Live Science Contributor) So essentially whatever colors an object absorbs defines what color it is because you are left looking at the color it reflects. As for water, the colors that it reflects are blues and violets making it appear a blueish color. Specifically for ocean and lake water, an even more blue or green hue is added to it because of particles that are within the water itself. These particles reflect their own blue or green colors often adding to what our eyes are picking up.

Another reason that large bodies of water appear blue and not clear is the actual number of water molecules. “Just how blue the water is depends on how much there is to absorb the light. For instance, water in a glass is clear – there aren’t enough molecules to really absorb the light.”(lifescience.com) So the amount of water also has a say in what color we are picking up. The more water there is, the more wavelengths there are that can be absorbed and reflected

To summarize, there are multiple reasons why the ocean appears blue, and why your cup of water appears clear. The ocean oftentimes reflects the color of the sky, and when the sky is clear can increase how blue the water appears. There is oftentimes particles in the ocean that also reflect a blue or green light. And lastly, there is simply so much more water molecules in large bodies of water that the number of waves absorbed and reflected increases. Hopefully the next time you are drinking a bottle of water at the beach, you will now know why it is crystal clear and the water you are swimming in is blue!