Immortality in the sea

Forget Transhuman, I want to regenerate like Dr Who, and this jellyfish. It can use a process of transdifferentiation to be immortal. So can a Planarian worm. I think that it is quite possible that people would ever decide to stop killing each other as a national pastime or group sport, we could see a time when humanity was very much like the Time Lords of Gallifrey, but with much cooler clothes and a new theme song. Now all we need is a phone box that will time travel and we are set!