Amy,
I swam as competition swimmer for years, we had some specially designed wetsuits that created drag in the water. Anyway, from having to wear one of these about once a week, I can say, something tight that won't bunch up. After a long time of wear if you had a normal swimsuit on you will develop the lines from where the fabric gets folded when this shifts blood rushes back into these areas, and goes from feeling like an itch (which you look pretty funny scratching) to actually creating a bruse. Not to mention these suits don't trap as much water there so you don't feel like you just pee'ed in you wetsuit all the time. (even if you didnt)
CR