This is the Maxis “Ruffled Tankini” turned into two separate items. Why should only adults be able to mix and match like they want?
The top is for girls (Swimwear, Everyday, Party, and Sleepwear), the bottom is unisex (swimwear and underwear). The top works nicely with a lot of the Maxis bottoms; some of the colour variants are matching textures/colours of this skirt so they can be combined into a dress (of sorts).
I went a little overboard with the recolours — there are 70 of them all in all, 43 tops and 27 bottoms — so I had to split the top into two catalogue entries (the swatch list was messing with the UI because it was too long). They are the exact same item though, only with the solid and two-tone colours in one thumbnail and the patterns and dots in the other.
TS4CASTools, s4pe, Milkshape, Paint.net, Photoshop.