Buying a Swimsuit
Swimsuits are, relative to a lot of menswear, forgiving garments to shop for. You don't need an absolutely perfect tailored fit, so long as the suit stays up when you dive in (and most have a cord at the waist to help with that).
That said, you shouldn't just grab whatever is cheapest off the Walmart shelf and call it a day. You are likely to only have one or two swim garments in your wardrobe at a time, so it's worth finding ones you really like.
A few key steps to doing so:
1. Know Your Active Needs
2. Know the Visual Impression You Want
3. Be Honest About Your Body