How to convince my parents to let me quit swimming?

In order to convince your parents, you're going to need a couple more talking points that are specific to swimming. So far, your main complaints seem to be (1) time commitment, and (2) high standards. (The only thing specific to swimming you complain about is cold water.) I know you feel strongly about this, but your use of hyperbole ("living hell", "hate it with a passion") is not helping your case. Obviously your school and family have access to resources that 95% of the world can only dream of having. Your reaction is that it's ruining your life. Please realize this only makes you sound like a brat. I can only guess that your parents are concerned about your future, so you need to argue your case in that way. Being on the swim team gives you great opportunity for personal growth, but at what cost? What other opportunities must you forego given the time commitment for swimming? Music? Community volunteering? (Trust me: "Stay up late and watch tv" or "Hanging out with friends" will not be nearly as persuasive.) In order to convince them, you will need to be able to identify what you *do* want to do in place of swimming.

I kind of know how you feel... I wake up at 4:50 AM for practice every morning and hate it, but in the end, I love the sport of swimming itself and always remember why I put myself through hard swim practices: I want to get better. If you like the sport itself, than I think that you should keep in mind why you go to practice. However, if you really don't like it and want to quit, than just tell your parents! I'm sure they'll understand. By the way, I actually have a friend in your exact position... she's been trying to quit for two years and her parents won't let her. Honestly, you need to say it straight, and not just drop hints. Be brutally honest, if that's what it takes.