We rented a car for the day so we could visit the Congaree National Park. A manificent place with huge bald cypress, tupelo, loblolly pine and others. These knees are roots of the bald cypress that erupt out of the earth. No one really knows why, it could be stability or to get oxygen. Here's a bit about the park from the web site.
Astonishing biodiversity exists in Congaree National Park, the largest intact expanse of old growth bottomland hardwood forest remaining in the southeastern United States. Waters from the Congaree and Wateree Rivers sweep through the floodplain, carrying nutrients and sediments that nourish and rejuvenate this ecosystem and support the growth of national and state champion trees.