Drawn by Izumi, this "beachification" is the reference sheet for the beach outfit Zoey will be wearing on a planned beach trip to the Southern California coast common to all routes.
You can spoil yourself a bit with the design document we gave Izumi if you want, but this is the first of 3 outfit reference sheets she's drawing for Zoey's outfits because they'll greatly simplify making the final sprite outfits for Myumi or TiltSHIFT.


Source: official Arknights art by Yui
It's inspired heavily by a blend of Arknight Ch'en's "Female Tourist C" and "Ch'en the Holungday" skins (I guess that's the right word, but the former is only a sprite and the latter is an alternative operator form?) and features a lot of moving parts/accessories that'll change, be removed, or added throughout the day because Zoey will ease up and stop being so reserved as she takes off more of her outfit and gets comfortable being looked at; those parts she are removing are:
Given the complexity of the outfit, I'm positive that clear references for the outfit and its various states was the way to go as they'll speak a thousand words more clearly to Myumi or TiltSHIFT and bridge the language barrier than my own words could.