Wow! Thanks for the wonderful comments. It actually makes me feel more confident about the whole onepiece business. Babyangel:
I found the fabric in the $1 section of Wal-Mart. Here's what I found from testing it out in water: It's stretchy (probably lycra/cotton/spandex) b/c it retains its shape pretty well and it also dried off really quick. I didn't use a pattern but I did use an old tank that fit me snugly.
then I laid boy shorts (I like the cut at the thighs) on top at the height I wanted the bottom parts to start
and traced around the outline. Cut then sew.