The water around Long Island, particularly on the South Shore and in the Great South Bay, is often murky or "tea-colored" due to a combination of geological sediment and high levels of organic matter. Unlike the Caribbean, where the sand is made of heavy coral calcium that sinks quickly, Long Island’s beaches are composed of fine glacial quartz and clay that stay suspended in the water when churned up by the Atlantic's strong surf. Additionally, the island's shallow bays are nutrient-rich environments where phytoplankton and algae bloom frequently; these microscopic organisms tint the water green or brown. Human factors also play a massive role; nitrogen runoff from fertilizers and aging septic systems fuels "brown tides" and "red tides," which further reduce clarity. While the North Shore's rocky beaches and the East End (the Hamptons) can sometimes offer clearer, turquoise-tinted water during calm periods, the natural "estuary" effect of the surrounding sounds and bays means the water will likely never have the crystalline transparency found in tropical or deep-ocean regions.