ronbeau:I wear Under Armor and it never bunches up. Other people mentioned that WalMart has a general version of Under Armor that cost less.
Speedo also makes something similar call Jammers that people have discussed here on ScubaBoard.
I would definitely prefer either if the items I mentioned to a bikini or a typical Speedo bathing suit.
I have the generic WalMart "under armour". It's okay, but it ain't under armour by any stretch. It's very thin and the waist band is very loose compared to the compression fit of the leg material.