Protected by surrounding coral reefs, lagoons of atolls form where the original volcanic islands sank beneath the sea. At Palmyra, the lagoons – including the open West Lagoon and semi-enclosed Central and East Lagoons, along with the dredged channel into West Lagoon -- provide a lush, fertile ecosystem supporting a staggering diversity of sea life. Tidal, oceanic, and wind-driven currents sweep through and across the reefs and into the lagoons, keeping the water clean and rich in nutrients.