Bahamian coastlines have undergone significant changes over millennia due to storm activity, sea-level fluctuations, and, more recently, human influence. Coastal features such as lagoons, ponds, creeks, and bights often form in response to environmental changes that alter seawater flow around and within islands. Sediment deposition can seal lagoon mouths, creating enclosed hypersaline ponds. During glacial periods, falling sea levels exposed sandy shorelines, which over time, hardened and, through continued wave action and rainfall, developed into jagged karstic rock formations. In some areas, dead and exposed corals have become integrated into the rocky shoreline. Periodic sea-level changes have also contributed to the formation of beach rock.