What is UP?! Cardi B announced a few weeks ago that she and hubby Offset were splitting ... then the Migos rapper made a surprise appearance at Cardi's concert and begged her to take him back ... and now the two are jet-skiing together in Puerto Rico?! How'd we get here?

Well as Cardi is in her hometown of San Juan, Puerto Rico to perform at the Electric Holiday concert and guess what -- Offset's there, too! They were photographed jet-skiing together in the island capital and while Cardi wasn't wearing her wedding ring -- hey, she was jet-skiing, what do you expect?! -- she WAS wearing a sexy white bikini! Will these two reunite officially? Whadaya think?