Buzz
The first time I set my eyes on the Caribbean Sea, I was absolutely amazed. Growing up in South Jersey, I was accustomed to the murky, almost brownish, slightly blue hue of the Atlantic Ocean. But this was a whole new world. The water was incredibly bright, vibrant, and seemingly transparent. It raised so many questions. What gives it that unique color? Why can I see my feet here, but not back home? Is the Caribbean water cleaner? Does the sun have more intensity down south? And why is the water greenish-blue near the shore and a deep navy blue a mile offshore?
Since then, I've traveled quite a bit and heard various explanations from people. Some attribute the differences in color to pollution, others to the level of salinity. While I do believe these factors, along with others, have some influence, the key elements are actually the water’s floor, its depth, and the microorganisms within it.
Let’s first explore why water often appears blue in the first place.
Illuminating the Concept
If you've ever been on a cruise, you’ve probably noticed that the further you venture offshore, the more intense and darker the blue of the water becomes (navy blue). This happens because, in deep waters, there is no sunlight reflecting off the sea floor, allowing the water to absorb most of the sun's rays. Water molecules naturally absorb reds, greens, oranges, and yellows, while reflecting blue.
“When sunlight strikes the ocean, some light is reflected back, but most of it penetrates the surface and interacts with the water molecules,” says NASA’s Oceanography Division. “The red, orange, yellow, and green wavelengths are absorbed, leaving the shorter wavelengths of blue and violet to be visible to us.”
Shifting Sands
As the water becomes shallower and light can reach the ocean floor, the type of seabed plays a role in the water's color. For example, the coarse Caribbean coral reflects light differently than the fine sand found along the Northeast coast. These variations in how light is absorbed and reflected influence both the visibility and the color of the water.
Any light that is not reflected off the surface water or the ocean floor is absorbed by something within the water. As previously mentioned, much of this light is absorbed by the water molecules themselves, but microorganisms that live in the water also contribute to this absorption. Another important factor influencing color are the particles and organisms suspended in the water. Phytoplankton, for instance, contains chlorophyll that absorbs red and blue light while reflecting green. If there’s a high concentration of phytoplankton in an area, the water takes on a greenish tint. The more phytoplankton present, the greener the water appears.
These three factors—depth, the composition of the ocean floor, and the life within the water (along with other elements like pollution)—interact to produce the color we observe. This same principle applies to lakes, rivers, and even craters. It’s all about what resides in and beneath the water.
While we often focus on the oceans, the world’s waters are not limited to just green, blue, or brown. Take a look at these spectacular, uniquely colored tourist attractions from across the globe. If you were impressed by the Caribbean’s greenish-blue waters, wait until you see the striking red and black hues of volcanic lakes that will truly take your breath away.
Laguna Colorada, Bolivia
Courtesy of Flickr user Valdiney Pimenta
The unique red color of this salt lake in Bolivia is due to a combination of red sediments and algae pigmentation, which is further contrasted by the white borax islands scattered throughout. Situated more than 13,000 feet above sea level, this lagoon is part of the Andean Fauna National Reserve and serves as a regular resting spot for various species of flamingos.
Kelimutu Volcano, Indonesia
Courtesy of Flickr user NeilsPhotography
At the summit of this volcano, three crater lakes exhibit strikingly different colors. Typically, Tiwu Ata Mbupu (Lake of Old People) is blue, Tiwu Nuwa Muri Koo Fai (Lake of Young Men and Maidens) is green, and Tiwu Ata Polo (Bewitched or Enchanted Lake) alternates between black or red, although these colors are known to change frequently and unpredictably. The two latter lakes are separated by a crater wall, creating a remarkable contrast when viewed side by side, especially when one is green and the other black, as shown in the photo. While no official explanation has been found, it is generally believed that volcanic gas activity triggers chemical reactions that bring nutrient-rich water to the surface, causing the color changes.
Lake Pukaki, New Zealand
Courtesy of Flickr user Peter Nijenhuis
Glacial erosion fills this lake with glacier flour, which consists of finely-ground rock particles, giving the water a frosty, cloudy-blue hue, often called glacial milk. Lake Pukaki covers an area of about 111 square miles and was formed when glacial debris, known as moraine, created a natural dam in the valley. Lakes with this milky appearance can be found in over a dozen countries worldwide. Although not uniquely colored, the Great Lakes are the largest glacial lakes on Earth.
