Here's the size chart for choosing the Watery Salmon Glide wetsuit for men. Measurements are taken with the suit lying flat and without stretch. The wetsuit will adapt and stretch both during use and in water, molding to your body as you swim. Choose your size based on the measurements you are closest to.
If you find yourself between two sizes, select the size where you hit most of the measurements. Generally, the most important measurements are chest and height (ankle to shoulder).
A wetsuit shouldn't fit too loosely; if you notice a lot of air pockets or "bags" around the suit, it's too large for you.