Masters swimmers that don't compete

I was just wondering if anyone out there knows of masters swimmers who don’t compete and that have achieved Top Ten Times, American Records, World Records, etc. in practice. I know that stories have circulated around about swimmers like Mark Spitz who have done this (although I think he did compete :)). I was just wondering if there are similar stories in the masters ranks. It seems to me that it would be highly probable in masters swimming because so many of its members do not actually swim at meets. Therefore, I would think there are people out there who achieve these (unofficial) times during a practice session and are relatively unknown. If you’ve got a story to share, please do.