The reason the ocean is blue is due to the absorption and scattering of light, NASA explains. The blue wavelengths of light are scattered, similar to the scattering of blue light in the sky, but absorption is a much larger factor than scattering for the clear ocean water.

The blue color of the water in the Gulf of Mexico—particularly in the deeper, central regions and near the Florida Panhandle—is primarily due to light absorption and scattering. Water molecules naturally absorb longer wavelengths of light (like red, orange, and yellow) more easily than shorter wavelengths (blue and violet). As sunlight penetrates the water, the "blue" part of the spectrum remains and is reflected back to our eyes. In 2026, the clarity of the water also plays a major role; where the water is "oligotrophic" (low in nutrients and algae), there are fewer particles to scatter other colors, resulting in a vibrant, deep blue. Near the coastline, however, the water can turn emerald green or even brown due to phytoplankton (chlorophyll) or sediment runoff from major rivers like the Mississippi. The iconic "Emerald Coast" in Florida appears green because the shallow, white quartz sand reflects the blue light through a layer of green-tinted algae, creating a stunning turquoise hue.