Here is the size chart for selecting the Watery Tackey Elite wetsuit for men. The measurements are taken with the suit lying flat and without stretch. The wetsuit will give with use and in the water, adapting to your body as you swim. Choose the size based on the measurements you are closest to.
If you find yourself between two sizes, select the size where you match the most measurements. Generally, the most important measurements are chest and height (ankle to shoulder).
A wetsuit should not be too loose, so if there are many air pockets or "bagginess" around the suit, it is too large for you.