Here is one more idea. Use an "emergency space blanket" for a backdrop. One will suffice for 3/4 length shots. You will need two or three to do full length.
There are two types of these blankets. The cheapest one appears to be nothing but a specialized type of mylar. These I have founds to be poor for background use because they just have too many folds and creases. The more expensive version has a silver side and an emergency orange side that is some type of synthetic fabric or something. This is the one I use for backgrounds. Here is a link to one on-line that I found. http://www.armynavysales.com/Merchan...egory_Code=BED
I have found them locally at a ****'s Sporting Goods and Sports Authority, but neither of them lists it on their web sites.
I don't have any swimwear samples, but this lingerie is pretty close. You can get a tighter look out of it if you really clamp the edges and pull it tight.