Beautiful babydoll dress or swim cover up, in a black eyelet by La Blanca by Rod Beattie. Deep V Neck in front with a cute little bow detail. empire waist ( elastic) and cap sleeves. Would be a cute top over leggings or jeans if you're taller. Looks and feels like cotton to me and probably a large to extra large but the size and contents tag was cut away so I can't be sure.
See measurements below.

Excellent preowned condition. I haven't seen anything worth noting.

Armpit to armpit across bust all round: 46"
Empire waist at elastic: 30" at rest up to 43"
length shoulder to bottom hem: 33"

Size: Large