Why Red Sea Is Red? (Color/Name Explanation)

Red Sea

Hello, explorers of the mysterious and the marvelous! Have you ever pondered over the intriguing names of places and their origins? One such enigma is the Red Sea, a body of water that has captivated travelers, historians, and scientists alike with its name and its beauty. But what’s in a name, you might wonder? Why is the Red Sea called “red” when its waters, to the naked eye, often appear a brilliant blue?

The Red Sea is a seawater inlet of the Indian Ocean between Africa and Asia. The Red Sea is 355 kilometers or 220 points, six miles wide at its widest point. Oceans and seas have various names, but one of the sea’s names, the Red Sea, has a reason behind it: red? The Red Sea is a seawater inlet of the Indian Ocean between Africa and Asia.

We’re diving deep into the coral-rich waters and the history behind this fascinating moniker. So, grab your snorkels (metaphorically speaking), and let’s go on a colorful journey to unravel the mystery of why the Red Sea is called red!

Why is The Red Sea Called the Red Sea?

The Red Sea is called so due to the reddish-brown color often observed in its waters. There are a few theories and explanations for why the Red Sea got its name:

Historical Story: One theory suggests that the “Red Sea” may have originated from ancient descriptions or accounts of the sea’s color. Historical sources, such as the writings of Herodotus and Pliny the Elder, mention the reddish color of the sea.

Reflection of Sunlight: The Red Sea’s unique geography and the presence of specific organisms contribute to its reddish hue. The sea is home to a high concentration of phytoplankton and cyanobacteria, which can contain pigments that give the water a greenish or reddish tint. When sunlight reflects off these organisms and interacts with the water, it can create a reddish appearance.

Translation from Ancient Languages: The name “Red Sea” may have been a translation or interpretation of ancient names given to the sea in different languages. For example, in ancient Egypt, the Red Sea was known as “the Great Green,” which could refer to the sea’s color or its perceived vastness.

Cultural and Symbolic Associations: Cultural and symbolic associations might have also influenced the name “Red Sea.” Red has significance in various cultures, often representing power, danger, or significance. The name “Red Sea” could have been given for symbolic reasons rather than directly describing its color.

Why is the Red Sea red?

The Red Sea derives its name from the reddish-brown color often observed in its waters. The main factors contributing to the Red Sea’s distinctive color are:

Phytoplankton: The Red Sea has a high concentration of phytoplankton, microscopic marine organisms that contain pigments such as chlorophyll. These pigments can give the water a greenish tint, which, when combined with the reflection of sunlight, can create a reddish hue.

Cyanobacteria: Another group of microorganisms called cyanobacteria, also known as blue-green algae, are present in the Red Sea. These bacteria can produce reddish or brownish pigments, such as phycoerythrin, contributing to the water’s coloration.

Suspended Sediments: The Red Sea is bordered by arid regions, and strong winds and currents can transport sediments from the surrounding land into the sea. These suspended particles, including clay, silt, and iron oxides, can give the water a reddish-brown tint.

Underwater Topography: The Red Sea is a narrow and relatively deep body of water with steep underwater slopes and canyons. Light reflecting off these underwater features can interact with the water column, enhancing the red color perception.

Sea has a different color that depends on the environment and internal factors. Water has no color, and every color we see is an illusion. Scientists have discovered the color varieties and given specific reasons for them. The Red Sea is not red. There are three reasons for the red color.

  • For bacteria.
  • For algae.
  • By scattering.

By bacteria

The Red Sea is a tropical sea with a huge number of coral reefs. No rivers connect this sea, which is highly salty with an average of 40% salinity—that means around 40 grams of salt in 1 kg of water. The Red Sea contains cyanobacteria named Trichodesmium erythraeum. These bacteria do photosynthesis and turn the Red Sea from bluish to red. They are also called “sea sawdust” because they form a reddish color and are abundant in the Red Sea.

We can see bacterium through the naked eye because they live in colonies or individual filaments where hundreds of cells are bound together. What makes these bacteria turn red is unknown and still under research. Phycobilin pigments may be phycoerythrin and phycocyanin for red and blue pigments.

These pigments may be the cause of Trichodesmium erythraeum. To summarize, the Red Sea contains a bacterium named Trichodesmium erythraeum, which gives it a reddish color. The bacterium is photoautotrophic, which means it depends on photosynthesis to make food.

In the same way, the black sea has a depth of over 150 meters, and its deepest layers have only sulfur bacteria, which produce hydrogen sulfide gas. It decomposes the dead organic matter of the sea and gives it a composted blackish color. The White Sea is white because it is covered in ice for 6-7 months each year. The Yellow Sea is named Yellow because it carries silt from the upper plains, giving it a brownish-yellow color.

By algae

Algal blooms deplete the water’s oxygen, discolor the waves, and release toxins into the water. They aren’t plants but a diverse set of organisms that can photosynthesize. This means they use sunlight energy to turn carbon dioxide into oxygen and sugar. They can be single-celled or multicellular. There is a rapid accumulation of a mass of aquatic Algae made up of mobile single-celled microorganisms known as dinoflagellates.

It means wheeling due to the nature of the tail-like projections that propel them through the water. The algae grow or bloom more rapidly than usual to consume nutrients that have suddenly risen from the colder depth of the ocean below. The red hue is down to a particular species of dinoflagellate or phytoplankton.

Dinoflagellates comprise most of the ocean’s plankton, along with the more abundant diatom algae. Although the rather startling appearance of a sea turned red, many algal blooms are entirely harmless.

However, you shouldn’t consume seafood following a red tide. A specific fleet of plankton can release harmful substances into the water. Some dinoflagellates can produce toxins when eaten by other creatures. The harmful substances then concentrate inside the creatures that feed on them. The billions of microscopic dinoflagellates create the red tide, which can also cause spectacular bioluminescence at night.

One species, the linguLoDinium polyedrum, can create its light. A chemical reaction occurs when the organism collides with something in the ocean. When an enzyme is called luciferase, the substance is called luciferin. Both are contained within the organism combined. This catalyst for a chemical reaction releases blue and red light flashes.

By scattering

Sunlight reaches the sea and mixes with water molecules, plankton, etc. Since the light waves are tiny, they interact with even the smallest molecules in the water and begin to bounce off. This bouncing process is called scattering. It depends on how large the molecule is compared to the wavelength size and small particles.

Their wavelength will scratch a red light more scatter than blue light of the sea’s internal environment. The other colors, like blue, will absorb water, and only red will scatter. So, the red will scatter sunlight in more directions than the blue, which creates a red color in the Red Sea.


We’ve discovered that the world is full of wonders, and the names we give them often carry stories, explanations, and a bit of magic from the past. The Red Sea’s name is a reminder of the natural and historical mysteries that our planet holds, waiting for curious minds to uncover.

Thank you for joining me on this aquatic adventure, delving into the reasons behind the intriguing name of the Red Sea. May your thirst for knowledge and adventure never be quenched as you continue to explore the mysteries of our world and the stories they tell. Until our next journey, keep diving deep into the wonders of our planet!

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Julia Rose

My name is Julia Rose. I'm a registered clinical therapist, researcher, and coach. I'm the author of this blog. There are also two authors: Dr. Monica Ciagne, a registered psychologist and motivational coach, and Douglas Jones, a university lecturer & science researcher.I would love to hear your opinion, question, suggestions, please let me know. We will try to help you.

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