Re: Want to do a triathlon but.....
If you think about it, everyone starts as a terrible swimmer, and some people have to work harder at one of the three sports, yours happens to be swimming, no big deal. You can get better at it though! It's a lot better to be bad a swimming because the potential is much greater, the better technique, the faster you go for the same effort. As for running, once you've maxed out your effort, your potential for improvement is not as great!
So I'd go for it, find a masters team and go for it! You'll likely do very well considering your strength on the bike and run.