I second the Zoot tri-racerback. I just bought one and absolutely love it. I took it for a test drive (without a bra) under my wetsuit yesterday and didn't feel it. I haven't run in it, but if I need something extra I'll probably use a Champion with wicking material.

Oh, and you'll go straight from the water to the bike without changing, so you do end up wearing the shorts you swam in for the whole time. I wear a Garneau compression short with just a little shammy.

Happy shopping!