I swim laps three times (thrice?) weekly, and it's really hard to find a bathing suit these days that is suitable for actual swimming, while simultaneously NOT looking like something your grandmother would wear. The problems can be narrowed down to three problematic trends.
Problem trend #1: The Tankini
The tankini is a great idea in theory. A two-piece swimsuit where the top comes all the way to the bottom, like a tank top? Perfect. No tummy showing, and you can buy a black bottom and several different tops, so it's like getting all these different suits. The problem here becomes obvious after you begin swimming laps in them: they have a tendency to float up around the waist, and eventually end up near your breasts anyway, so you may as well be wearing a bikini for all the coverage you end up with.
Problem trend #2: One-pieces for grannies
A friend of mine recently told me that she was shopping for a swimsuit and wanted a one-piece. She's got a fantastic figure and would look great in a bikini, but she is not that type of girl at all. The problem was that all of the one-piece bathing suits she found in the stores looked like something a 60-year-old would wear on the chaise lounge beside the pool. She originally thought it was something a 40-year-old would wear, and then she realized that 40 is just around the corner and she still wouldn't wear that hideous thing.
Problem trend #2: Lack of breast support
Let's face it- my boobs are big. Huge, actually. And while water does have certain gravity-defying properties, it's still not good to have a lack of support. Something has to keep the great, pendulous things in their proper place. I recently purchased a bathing suit through mail order (see Problem trends #1 and #2 for why I resorted to mail order) and I had been in the pool for half a lap when I realized my right breast was floating free of its fabric-y bonds. I was mortified, until I realized that no one was looking. Then, I was even more mortified. Needless to say, that suit was returned to sender post haste.