Don't worry about what the other people are saying. "you can't do it in 4 years"
Bull.
Over 300 athletes started training 4 years ago and made it to beijing, including 10-50 that made bronze medals or higher.
(one even got gold from what I remember, a runner)
A good example would be the american pole vaulter. She was sitting down watching the olympics 4 years ago and she wanted to do pole vaulting, In 2008, she won the pole vaulting silver medal. And the only reason she lost was due to the first place being a world record holder, (Who broke it again in beijing)
You don't need time, you just need dedication.
If you want, try pole vaulting.

(And Charxx, the reason you're not olympic level is not because you're not good enough, but you're too young specifically for swimming, if you look at michael Phelps / etc. You need to be at least 18+ With a long lean body for hydro-dynamics.)