Largest coastal lagoon

Lagoa dos Patos ("Duck Lake"), located near the shore in Rio Grande do Sul in south Brazil, is around 280 kilometres (174 miles) long and extends over 9,850 square kilometres (3,803 square miles), separated from the Atlantic Ocean by long sand strips. It has a maximum width of around 70 kilometres (44 miles).

While Lagoa dos Patos is the largest coastal lagoon, the largest atoll lagoon occurs in New Caledonia in the South Pacific.

According to NOAA: "Atoll lagoons form when an island completely subsides beneath the water, leaving a ring of coral that continues to grow upwards. At the center of the ring is a body of water that is often deep. The combination of coral growth and water creates a lagoon. It may take as long as 300,000 years for an atoll formation to occur.

"Coastal lagoons form along gently sloping coasts. They are generally shallower than atoll lagoons and tend to be separated from the ocean by an island, reef, or sand bank. Most of the time, coastal lagoons are connected to the ocean by an inlet. Sea level rise, the amount of existing sediment and tidal range all contribute to the formation of coastal lagoons. Younger and more dynamic than atoll lagoons, coastal lagoons may have shorter “lifespans” due to their exposed locations on the shore."