I wet suit will help. I have a semi dry wet suit and I stay warmer if the water doesn’t get in. Some Gumbie suits are made with neoprene like wet suits but their seems are sealed and they have built in boots and wrist and neck seals. A dry suit only works as good as the air within it. I’m with Lat in that I think a good thermal garment will give you the best protection and ease of movement. Even a good under garment can be made useless if it’s compressed at depth.