A range of men’s neoprene wetsuits
The thickness of a wetsuit will directly affect how warm it is. A 5mm suit will be warmer than a 3mm wetsuit and more suited to months when the water is colder.
For a wetsuit to work well it should be quite a tight fit as it needs to trap a layer of water between the neoprene and your skin.
If the wetsuit is a loose fit it may well be more comfortable when you are out of the water but it will not keep you warm.
Full length wetsuits are generally warmer.
You may prefer a farmer john style though if you need flexibility in the arms for sports like kayaking.