These were recommended to wear in any t-shirt, light weight shirt or bathing suit if you wanted to keep your nipples from showing through.  I find they work excellently!  Unlike the pads I had to wear while nursing, these definitely are NOT noticeable.  The cotton  pads always wrinkled, these actually adhere like a suction cup does to a mirror, but much more gently.  They don't slide and come off easily at the end of the day.  I wash mine and air dry them after every use and wear them all day long. Mine have lasted in excellent shape and I do not find they create any odor or make me swet. However, I do admit I have not tried them in the pool, but I really would be surprised if they slid around.  That having been said they are not meant to be worn instead of a bra, but inside of one.  They do not offer support of any kind but do exactly, and well, what they were intended to do, give you a modest look despite age or weather.