What caused the Everglades of Florida?

In times past, many of our land areas sank below sea level and became swamped With shallow water. In other places, the floor of the sea rose higher and became dry land. Through the ages, vast areas have been flooded and drained time after time. The peninsula of Florida is a low strip of land which once belonged to the sea. Ages ago, the peninsula began to rise and for a while was a swampy region of soggy islands and salty lagoons like the everglades. In time, the water drained from most of the peninsula, leaving dry land but the everglades still belong to both the land and the sea.