If you are thinking about making one, I think what you want is either nylon/spandex or polyester/spandex, not cotton/spandex. I'm certainly no expert, so feel free to correct me if I'm wrong. The first suit I made was a polyester/spandex blend, but all of those fabrics above are nylon/spandex. It's a little thicker, but the poly/spandex worked just fine and might be easier to find.
After searching around for swimwear sewing tips, I came across this site. I wish I had seen their tips before. I had bought some fancy elastic that I thought was the right kind, when in fact the regular elastic I had in my drawer says right on the back that you can use it for swimwear. Go figure!
Before I had a chance to really read over the Creative Chicks tips, I tried making a pair of bottoms for myself. They came out pretty good, though a little small.
I folded the top over twice and then did a zig-zag. It looks much nicer than the leg openings which I just folded once.
The seam flattens out when it's on my body, but is still a little wonky. With the Creative Chicks tips in hand, I'm confident the next suits will be just right.
Are you inspired to make your own yet?