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Asking yourself why is water clear may sound random, but understanding the science behind water being blue or transparent also means ensuring clean water!

We often see blue or bluish-green shades of water in places like oceans or lakes, while the water flowing from our faucet up close at home is transparent. It may sound completely out of the blue, but knowing why is water clear or not can help us identify when it’s polluted or clean.

What makes ocean water appear clear in some areas?

Wayer is colorless, yet it can look crystal clear in some areas while others seem murky or grayish due to an occurrence called upwelling. The earth’s rotation causes the ocean to move. As a result, warmer surface water transfers to the sea and is replaced by colder sediment water underneath.

The shift in water can cause life forms and particles to shift in the water, causing murky-grayish water. No need to fret! Murky doesn’t necessarily mean dirty water; it’s even richer in nutrients than clear water. It’s filled with living organisms like phytoplankton (algae) and zooplankton like jellyfish and other sea critters.

Finer particles of salt, tiny rocks, clay, and sand can also add to the grayish color as they can move and stay afloat for a long time.

Areas like the Mediterranean sea, the Philippines, and Japan have crystal sparkly clear. On the other hand, west coast areas like the U.S., Mexico, and Chile have grayish-blue water.

Reasons why we see the ocean water blue while it is clear:

Although the ocean water appears clear, it looks blue from afar. Why is the ocean blue? That’s because water molecules can absorb all shades of red in the electromagnetic spectrum except for blue, leaving a crystal blue sparkling color. 

Ocean or seawater can also take a bluish-green hue due to green light bouncing off floating sediments such as plants, bits of coral, shells, and other solid particles that can affect the color of the ocean. 

Sediments are solid materials that can be moved or placed; examples are rocks and other minerals. All these can affect the color of the ocean, especially when disturbed by rain or upwelling.

Why the Ocean scatters blue light:

Water may be clear, but far away, we all see it in rich blue because water serves as a sunlight filter, said the National Oceans Service (NOA). It absorbs enough light from all red or warm wavelengths but cannot be transparent to blue ones. 

However, visible light cannot entirely pierce the ocean due to its depth. Light can barely pierce shallow until 656 feet below water. No light reaches below 3,280 feet deep underwater. 

The Library of Congress says that the color blue wavelength is transmitted across it. Water molecules scatter light by rapidly absorbing light waves, then re-emit them in different directions, causing them to reflect our eyes. On rare days, the ocean can also mimic the sky blue colors when it’s incredibly still, like a mirror facing the sky! 

What makes sand on certain beaches different colors

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Have you ever wondered the answer to why some beaches have gray or white sand? Why do the Bahamas or Bermuda islands have luscious pink sand? Sand is a coastal sediment that comes in different colors and can change the overall color of a beach. According to the National Park Services, the sand’s color depends on its parent rock from which the sediments eroded.

The parent rock may be from a local source like a nearby cliff or bluff. These can come from farther places. An example of this is the Mississippi River delta sediments shipped from Montana.

Some minerals also have natural pigments that affect a beach sand’s color.

Composition of minerals and rocks

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Let’s take a quick science lesson! There are three main types of rocks based on the British Geological Survey:

Sedimentary rocks

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Fragments from eroded and weathered parent rocks consisting of silt, sand, dead plants, and even animal skeletons!

Igneous rocks

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Cooled rocks formed from the magma of volcanoes.

Metamorphic rocks

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Originally sedimentary or igneous rocks that underwent extreme pressure and temperature — formed into something new.

We’ll be focusing on sedimentary rocks! These are often minerals like sand, mud, crystals, or pebbles that break from their parent rock through erosion and are carried away by the river, wind or manually taken away.

You can often find these on a lake, sea, or beach. Some sedimentary rocks are also from shell fragments which can influence the color of the sand on a beach.

Sedimentary rocks can also come in other colors that can change the beaches, and influence the ocean color! Some are color-producing minerals like: 

  • Hematite (red)
  • Limonite (yellow)
  • Magnetite (black)
  • Olivine (green)

Orange sand also exists through a combination of, limestone, and iron-rich materials, orange organisms.

All these ingredients combine with upwelling and light to ultimately affect the mesmerizing color of sea or ocean water!

Does pollution have an impact on the color of ocean water?

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Unfortunately, factors like pollution can affect the clear blue color of the ocean. Chemicals and waste dumped into the water can tamper with the process of water molecules absorbing light. 

There are also invisible pollutants that float around. But man-made pollution is known to highly affect the marine system; this includes oil spills, detergents, herbicides, pesticides, industrial chemicals, and sewage. There have also been cases of dynamite fishing or fish bombing known to contaminate and destroy coral reefs.

Not only pollution but also climate change or global warming, in general, can change the color of the water. 

For example, the Philippines is rich in mangroves and forests. One of their strongest natural habitats, Sierra Madre, or its largest mountain range, shields the Philippines from typhoons and other calamities, lessening the casualties in both land and water. As a result, the coastal areas of the Philippines are abundant in undisturbed crystal clear water. 

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If the Sierra Madre were to be burnt or cut down, this would leave the Philippines vulnerable to upwelling that can ruin its waters. That goes for all forests protecting land and water from disastrous upwelling.

Conclusion – Why is water clear?

Caring for our environment, especially for small and large bodies of water, is one way of upholding our well-being. Knowing why water is clear like glass means how much we should take care of our marine life to preserve crystal-clear water and the natural process of nature to maintain the beautiful bodies of water around us.

Our source water comes from springs, dams, and other bodies of pure water. Whatever we throw into it goes back to us. Keeping our marine life clean by preventing contamination is a way of keeping our quality and other species’ quality of life healthy and balanced.

If we are kind to nature, it is kind to us in return; especially the ocean.