About a week and a half ago I took my lab swimming and I started his dock diving training, he did awesome and had a blast, fetching his toy in the water and jumping off the low dock, well after we went back home I noticed he had gotten what some people call 'swimmers tail' also known as cold or limp tail. It took a week for it to be totally back to normal, it has happened before but was better in 2 days. He loves to swim and now I'm worried whenever I take him dock diving or swimming that this will happen to his poor tail, is there anyway I can prevent this, like ways to strenghten his tail? Thanks!!