Much of the brown color you see along the coastline will be a direct byproduct of rainfall and organic runoff. Drive a few miles away from the nearest major inlet and the water will be much clearer.

The water in Destin, Florida, is famous for being "emerald green," but it can turn brown due to two primary natural causes: tannins and algal blooms. After heavy rainfall or a tropical storm, freshwater from nearby spring-fed lakes and the Choctawhatchee Bay flows into the Gulf. This water contains tannins—natural organic compounds from decaying leaves and pine needles—which stain the water a tea-like brown color. This is a harmless ecological process and doesn't signify pollution. The second cause is Red Tide (specifically the algae Karenia brevis). During a bloom, the high concentration of algae can discolor the water to shades of rusty brown, red, or dark green. Unlike tannins, Red Tide can be harmful, causing respiratory irritation for people on the beach and posing a risk to marine life. In 2026, local authorities monitor water quality daily; if the brown color is accompanied by a "rotten egg" smell or dead fish on the shore, it is likely a harmful algal bloom. If it is just a dark "tea" tint after a storm, it is simply the natural result of Florida's unique coastal drainage system.