Fashion for Moms: Post-Pregnancy Swimwear
Well, you've heard it a million times: Wear black and dark colors. It works!
I also like tankinis, which dip in the front and cover your tummy. Pick something with a higher-cut leg line in the front and good back coverage. A higher leg line gives the illusion of a longer, thinner leg, while good back coverage assures it will not slip and be uncomfortable.
Also think about buying a cover-up skirt, and make it drip-dry in case you have to make any unscheduled dips while running after the kids.