That's an incredible Nami fanart ! I love it

I think her breast is suppose to be a bit bigger than that, but wow very nice art.

Yeah her tits would be bigger, but it's still rather awesome.

It's a model of her from the early volumes/episodes.

If you watch through the series, her chest size changes a lot. Even Oda, the artist has said that he's not sure how big she is, that he changes her as he sees fit arc to arc.

Also... that's a figure/model. A picture of one that was photoshopped very well with a background and such. I love the picture and have the figure myself. Nice Job.