My daughter is very slim but wears a size 5-6 due to her height. I bought her a size 4-6 pink leotard for ballet and it is too small (tighter than a leotard and cuts into her butt and shoulders). It's also transparent, but I like the material it's made of. It's stretchy (much like a bathing suit) and I don't have to worry about it rubbing like cotton. I gave 4 stars because I think that once I got a size up it would be the perfect swimsuit for her (once I can find some nude underwear for her).
Hollhoff Gymnastics Playgrounds Shorts - Breathable Clothing for Girls
48 Review
Amazon Essentials Little Short Sleeve Leotard Girls' Clothing for Active
61 Review
Thermajane Girl's Cozy and Comfy Thermal Underwear Long Johns Set with Fleece Lining
46 Review
Pack Athletic Performance Basketball Drawstring Girls' Clothing
48 Review
Fancy Girls Communion Dresses White Girls' Clothing in Dresses
53 Review
Castle Fairy Pageant Wedding Communion Girls' Clothing for Dresses
53 Review
Rainbow Toddler Princess Sleeveless Sundress Girls' Clothing and Dresses
57 Review
Amazon Brand Sleeveless Unicorns Metallic Girls' Clothing in Dresses
75 Review