What is the closest beach to Atlanta Georgia?

If you are talking about the Atlantic, probably Jekyll Island.

Not quite. While Jekyll Island is my preferred destination in GA, there are a couple of beaches that are closer to the ATL:

259 Miles, approx. 4.5 hours, Wilmington Island, GA, which is close to Savannah

280 Miles, approx. 4.5 hours, Hilton Head, SC

290 Miles, approx. 5.5 hours, JEKYLL ISLAND, GA (If you have a heavy foot you can do this one in about 5 hours easy. I make it in 5.5 and I live an hour north of ATL)