Well, technically, the Geechie, or Geechee, is what the Gullah people call themselves. They are the direct descendants of African slaves, and live along the coast of southern South Carolina and Georgia. They speak a combination of some african dialect, french, and english. It's confusing to listen to, but you can make out about every other word and get the gist of what they are saying. They have managed, for the most part, to keep their heritage alive and are a very colorful, no pun intended, people.
That guy in the video would also be considered a Geechie, but it's different than the Gullah. His people are among the first white people to settle in the lowcountry of South Carolina. They are Europeans, but I don't know where from, exactly. Could be Scotland. Many of those settlements date back to the late 1600s, early 1700s. It was tough country back then. Lots of hostilities with the natives.
I do know that their dialect was influenced by the Gullah and the French-Huguenots. At any rate, they speak very distinctly. The fellow in the video is a classic example, but some of them speak with a much heavier accent. A lot of those little towns have not been influenced very much by outsiders, so the way they speak hasn't been diluted over the years.
The area I'm talking about is the lower quarter of South Carolina and into Georgia. Charleston has it's own distinct dialect, as does Savannah. The Charleston dialect sounds very different from the surrounding rural areas, because of the influence of Sephardic Jews, from Spain.
Unfortunately, the dialects and customs get diluted over the years. People move in from elsewhere, and, while they might pick up a hint of an accent, they essentially corrupt the original. To find the genuine dialects, you have to go to the small settlements, where there is no reason for an outsider to move to.
I live in the opposite corner of the state. We have our own distinct dialect and unique history. Where I live was once the domain of outlaws and bootleggers. The city folk used to scare their children with tales of the "Dark Corner of the world". Sadly, our history and dialect is fastly fading. Our land has been bought up by developers who have turned it into a vacation home paradise for wealthy northerners. You wouldn't believe the beautiful country that has been closed off to the local people here. That's a whole other infuriating tale, though.
My own accent has changed due to the fact that I lived most of my adult life in Alaska and Washington. I did live in Louisiana for a couple of years, but I held strong and didn't let that influence me too much.