Vintage White Cover-up w Embroidery Detail & Tie String

No tags, might be homemade? Definitely synthetic, maybe nylon? I bought it thinking I could use it as a swim coverup, but then I worried repeated exposure to chlorine-treated or saltwater could cause yellowing or other damage since I don't know the actual composition of the fabric. As such, I really don't have any use for this. It's in very good condition, my home is smoke free with pets who aren't allowed in the dressing room.