So my lab retrieves, is not gun shy, is extremely obedient, but cannot stand those days when it is 25 degrees and the lake is cold. I bought him a vest, and it seemed to help a little, but he just refused to retrieve when its cold. He will get in to about chest depth but wont go further. If it's about 50 outside, he does great but with the colder weather I don't know what the problem is. I've hunted with other labs that do it without any equipment and have no problem, so I'm not quite sure what to do at this point. Any suggestions?