This swim dress is a loose, flowing style and runs large. Size down one size on this style. 

Small:  42" bust 

Medium:  46" bust

Large:  48" bust

XL:   50" bust 

2XL: 52” bust

3XL: 54” bust

 
46” length shoulder to hem. Lady in photos is 5 ft 8” for size reference around 160 pounds wearing a size small.