Green’s Dictionary of Slang

(US black) sexual intercourse.

1978		D.C. Dance Shuckin’ and Jivin’ 207: [T]his couple drove up, and they went threough the bushes and they done the Sandy Bottom Shuffle!
2022		J. Hannaham Didn’t Nobody Give a Shit 255: [They] got the nerve to be doin the Sandy Bottom Shuffle at his wake.