Finding a wetsuit that fits you like a second skin is 90 percent of the battle. Seals, seams and zippers: none of this matters if the wetsuit doesn't fit. Gaps in your arm pits, spaces between your legs, behind your knees or in the curvature of your spine will let water in and pump it around the inside of your suit, literally sucking the heat out of you.
A properly fitting suit encompasses your body with no gaps or spaces. Unfortunately, finding such a fit can be easier said than done. Everybody has a unique shape, and every manufacturer's definition of Small, Medium, and Large seems to be different. Some suits tend to be designed for muscular divers, while others fit lean divers better. Some manufactures offer a dizzying array of sizes, while others stick to the basics. Bottom line: to get a snug-fitting suit you're going to have to work for it. That means trying on as many suits as you can. Find a manufacturer who caters to your body shape, and who hopefully offers the suit you like in a lot of sizes. Then try them all on until you find the perfect fit. Remember, wearing a snug-fitting suit with no gaps or spaces, you'll burn less energy and stay warm longer. So if you just can't find a stock suit that will do the job, many manufacturers are willing to custom cut a suit to match your unique measurements.