C.A.
I have used the Kushies swim diapers. I really like them because they have leg gussets to hold in all the poop. I have used this brand of swim diaper with both of my breastfed babies. =) The cloth diaper suggestion is also good. You don't need to necessarily buy a pocket diaper, you could just get a diaper cover like bummis superbrite, that will definitely hold in that messy bf poop. =) You can find the bummis at the Nickis diapers link from the other poster, and you can find kushies at diapers.com.