The last time we had our cat shaved, the mobile groomer noticed what she called a water bubble. She mentioned she could poke it and squeeze if we wanted. We did do that and it was smaller. However 6 months later now it's back and maybe bigger. The cat is anout 17 years old and I would like to know what causes this. She is strictly an indoor cat by the way. Would the vet be able to do anything more than the groomer does at no charge?