If you have large breasts and are plus sized, you should be able to find a swimsuit with good suppot from a plus sized store as other posters recommended. If you are large breasted but thin, look for a bikini top that has underwire (it will look pretty much like a bra).

I also have to add that I *highly* recommend buying swimsuits online or by catalog. I work in a retail store and lingerie is one of my departments. I sensor underwear so that it can't be tried on (we damage out any underwear or swimsuit bottoms that are returned) but we have to sensor the swimsuit bottoms so that they can be tried on. I won't bother to gross you out with a description of the things we've encountered over the years.........I'll just say that I will *never* buy a bathing suit in a store :::::::::::shudder:::::::::::::::