For swimming workouts I would recommend a one-piece swimsuit. I found a couple of links from Livestrong that have some good information regarding your question. As for the brand, I leave it up to you:
I hope this helps.
For swimming workouts, women should wear comfortable and flexible clothes that don’t expose their body too much. It raise their confidence and make them feel relax while swimming. One piece swimsuits are fine to wear for swimming workouts. If you wish to buy such swimwear, go online and see the collection of some shops like http://www.leelach.com/modest-swimwear-for-women/modest-swim-dresses/sla… that shows its different pattern, color, shape and size inside one roof. Such swimwear will protect your body part from UV sun rays too.
Though nothing is perfect 🙂 I like a one piece Nike, Speedo the best. Tyr is great too with a junior fit. These are all a must try on!
I can size up at least once on the above brands and can go another 3 sizes. For instance: If size 6, buy an 8, but 10, or even a 12 fit great.
If swimming a lot, pricier suits are worth the investment because they WILL last. Many times I’ve found them at the local T.J. or Sports authority. The company Karin mentioned above is great for any type of body. However the turnover time when ordering isn’t quick.