I have a slightly different take about modest swimwear than most of the people writing about it seem to. Personally, I think people participating in an activity that are clearly dressed to participate in that activity appear more modest than otherwise.
Thus, I have no digs with the women's Olympic swim team. They are there to swim. Of course they look nice - they're healthy young women wearing more-than-skintight clothing. But they aren't in those clothes for attraction, they're there for a reason.
I have been able to bodysurf a bit this year, my kids have finally gotten big enough they don't have to be hand held every second in the surf. I wear a slightly skirted suit from Target with a rashguard... basically I'm wearing a micromini with a sleeveless tshirt. I've previously noted that the skirt - even though it is fairly form-fitting - will drift up eventually. (This is okay, there's a suit under it). But the other day when I caught a wave, the skirted portion of my suit made it up to waist height. Still a suit underneath, I wasn't breaking any laws (and anyway as a native Cali girl, my attitude is "put it back on and get on with your day"), but it made me SERIOUSLY question the true modesty of a skirted suit in the ocean.
I guess it makes sense. My dad was always death on any slightest hint that I might want to wear a tshirt into the water. He considered that a one-way trip to the morgue - ocean water catches extra material like a sail, and thick knit is heavy when waterlogged, which is another reason to avoid it. My rashguard isn't a problem - some of that is the material, and some of that is that it's reasonably fitted.
But if you're bodysurfing, you're presenting your lower half to the force of the water - that force is what drives you to the shore. If I'd ever stopped to think about it, of COURSE the water is going to get up under any skirted thing and rearrange it.
Fortunately I've never gotten around to making a swimsuit for myself.... I think my course just got corrected.
For the rest of you shopping? I'd recommend board shorts and a rashguard over whatever swimsuit you like. But no extra fabric ... it's *not* modest, being disrobed by forces of nature is never modest. ;)