Using this as a workout top may be a little bit revealing, but for small and mid-size busts, it will stay put... with some caveats. Make sure the knot at your neck is secured - double tie it; the smooth material of the top will not hold with just a single knot, especially if you are in motion. If you were lying on the beach and getting a tan, it would stay in place just fine... but if you were jumping around in the pool or working out at the gym, the single knot will untie itself. Make sure that the top is worn snug; the fabric on the back strap simply slips over the metallic hook on the other side, and there is no clasp or closing mechanism whatsoever. Knock on wood, I have evaded the situation, but it is something you should be aware of when deciding if you want to use this as a workout top.
Even though I have mentioned a couple of possible issues with the wear-ability of the top, for me it sat just fine, and I had no problems whatsoever.
It is not wicking at all, so it will not be good for any activity that may cause chafing. However, due to the smaller amount of fabric involved with this top, it doesn’t really have to be super-wicking for most activities. We're not running in this top, after all.
As for the bottoms, they will stay in place pretty well, with only a little adjusting along the way at most. The bikini as a whole is absolutely gorgeous, and is very wearable for everything it was intended for and more.