I agree with Deblas. If you look back ( Arlong arc), Nami is typical 5 foot 10 inch girl. During Water 7 acr she seems taller. Either that or they are making parts of her body out of proportion. It could be that camera focus on her is either too close and they want to show her larger than life during this emotional part of the story. She seems almost as tall as Robin in the last episode.