Per SC Code 23-31-205:
"Concealable weapon' means a firearm having a length of less than twelve inches measured along its greatest dimension that must be carried in a manner that is hidden from the public view in normal wear of clothing except when needed for self-defense, defense of others, and the protection of real or personal property."
There's no requirement for a type of holster. You can carry in a pocket holster, inside the belt holster, outside the belt holster, shoulder holster, smart carry, thunderwear, off-body carry (purse/murse) or whatever floats your fancy. You can even carry "mexican carry" (no holster) although I don't suggest that as it is unsafe.
Realize that SC is one of only a handful of states (around 7, last I checked) that don't permit "open carry." So SC, FL, TX, and the usual anti-rights states (MA, Cali, etc) are pretty much the exception to the rest of the country re open carry. Only in a few states -- like SC -- is inadvertent exposure of your lawfully carried sidearm a crime.