Without too much of a history lesson, a Geechee or Geechie (not Geechy) person is someone of a Gullah
descent. Gullah is the mixture of the English and African languages, that was spoken by slaves who were required to learn english, but still didn't want the masters to know exactly what they were saying. However, unlike the Gullah
link indicates, Gullah was actually widespread along the coast. It may have originated in Charleston, but there are many gullah civilizations located right in Beaufort, SC. The Geechee language is the derivative of Gullah, that has a creole, southern, and carribean twang to it. It still chops up the English language like Gullah, allowing someone to say more with less words, or eliminate excessive mouth movement.
The Geechee language plays a large part in the culture, which is better left for a definition to itself. The largest, active Geechee culture is located in Charleston, SC and it's surrounding areas, and proudly celebrated through such festivals as Moja Arts
. There is also a booth in Northwoods Mall, N. Charleston, that sells the clothing line, Geechee Gear. Such history can be discovered with a simple Google search. Although there's not enough people to make it a noticeable presence, the Geechee culture does stretch down the southern coast, touching Beaufort, SC, Savannah, GA, and other cities/towns down into Florida.
The most similar relation to a Charleston accent is that of the Caribbeans (though not nearly as strong) or New Orleans.