Why do Rebecca's breasts appear polished/shiny? I don't understand this image: 



If you look at her headgear, you'll see that it's polished and has that clean shine. But what's up with her breasts? They appear to be shining or they look polished, just like her helmet. I don't watch One Piece. So I don't know if she has shiny breasts, or if she polishes them. Can someone please enlighten me?
This picture shows Rebecca fighting in the Corrida Colosseum in  Dressrosa at the Mera Mera no Mi Tournament.

I the One Piece Wiki abpout Rebecca it's said:


  She is a fair-skinned, slender, curvaceous and very well endowed young girl


So we can assume that Rebecca has a very smooth skin. 
Since fighting is very sweat-inducing, we can say that her body is covered in sweat. 

Sweat + smooth skin = shiny skin in the right viewing angle