Tybee Island, Georgia, is a popular destination, but its ocean water often appears murky or brown, unlike the clear, turquoise color found elsewhere. This distinct appearance is a normal characteristic of the local geography and ecology. The color results from a combination of physical sediment carried by a major river and natural organic compounds from surrounding marshlands.
Influence of the Savannah River and Coastal Sediment
The primary reason for the brown appearance of the water is Tybee Island’s location directly adjacent to the mouth of the Savannah River. This major river system drains a large watershed, carrying immense amounts of fine silt and clay downstream to the Atlantic Ocean. The constant flow deposits this suspended material, known as sediment, into the coastal waters surrounding the island.
The river’s output creates high turbidity, which is the measure of cloudiness caused by fine, suspended particles. As the tide shifts and coastal currents move, this sediment-laden river water is mixed and distributed along the Tybee shoreline. This physical material absorbs and scatters light, making the water appear brown rather than transparent.
The Georgia coast is characterized by a low-country landscape where loose sediment is abundant. This geography ensures the water always contains a high concentration of particulates, especially near the river’s outlet at North Beach. The water becomes noticeably clearer just a few miles offshore, highlighting the localized impact of the river’s sediment load.
Role of Marshlands and Dissolved Organic Matter
A secondary factor contributing to the water’s color is the vast network of salt marshes surrounding Tybee Island. These marsh ecosystems are rich in decaying plant matter, which constantly leaches natural organic compounds into the water. This material is collectively referred to as Dissolved Organic Matter (DOM).
The decay process releases humic acids and tannins, the same compounds that give tea its brown color. The water absorbs this natural stain from the marsh environment, resulting in a brownish-yellow hue often described as “blackwater.” This staining effect provides a chemical contribution to the overall dark color, separate from the physical sediment load.
The expanse of the Lowcountry marshlands ensures a continuous supply of these organic compounds to the coastal waters. When this stained water mixes with the sediment-heavy flow from the Savannah River, the combination produces the deep, murky brown color typical of the Tybee Island shoreline.
Clarity vs. Cleanliness: Safety Implications
The natural brown color of Tybee Island’s water is primarily an issue of clarity, not cleanliness. Clarity relates to how transparent the water is, which is poor due to high turbidity and staining from Dissolved Organic Matter. Water quality refers to the health and safety of the water for human contact, assessed through scientific monitoring for contaminants.
The Georgia Department of Natural Resources (DNR) and the Coastal Health District routinely monitor water quality throughout the swimming season. They test the water for the concentration of enterococcus bacteria, which serves as an indicator of potential fecal contamination. If the bacteria level exceeds the EPA’s recommended standard of 70 colony-forming units per 100 milliliters of water, a public advisory is issued.
These advisories alert the public to a possible health risk and recommend against swimming, but they do not mean the beach is closed. Elevated bacteria levels are often linked to non-natural events like storm water runoff or animal waste, which are distinct from the natural causes of the brown color. The DNR collects samples weekly and releases the test results the following day, allowing the public to check local advisories.
While the usual brown color is not a sign of pollution, heavy rainfall can occasionally lead to temporary water quality concerns. Storm water runoff can carry pollutants from land into the ocean, sometimes resulting in a temporary advisory. However, the consistent, year-round murkiness is a natural characteristic of the coastal environment.