This depends on the style and the maker, and whether they tend to run long or short in the body, I find. I generally size up one in a one-piece suit, but any more than that and they bag in the bum. I also prefer a long, as I have a long torso, so suits that are built shorter in the torso simply do not work because as I size up they become baggy by the time they are long enough in the body.
Don't second-guess yourself, Neel. You bought the best of the bunch, and sometimes that's the best we can do. Wear it proudly, test it out, and you will know better next time based on how this one fit in the water and out. Everyone has the right to swim, so don't be shy. And while halter styles may not be the most comfortable for many people, they generally are quite flattering, so you will likely look great!
