Hey, I think that's great!! You were able to finish a 1/2 mile swim in cold, open water doing the dog paddle in panic mode (I couldn't do that!). You're be fine! I'm no natural swimmer, I learned to swim (freestyle) correctly when I was 49, and that's when I did my first triathlon, which was the California 70.3. My first time in the cold ocean I panicked for a little bit also, but you always have the choice to exit out if you want and there's nothing wrong with that. But, if you become determined (to do it), just put your head in the water and practice your stroke, like you've done thousands of times before, and you will be fine. Remember, keeping your head down in the water saves you a lot of energy and improves your swimming efficiency tremendously. In your swim training always practice breathing on both sides so you will be comfortable with either side in open water (sometimes due to waves or chop it's better to turn to one side or the other). My final advice is "don't think about it", you are in this for fun, I take it you're not a professional. So, enjoy it all, enjoy the training and the challenge... if you don't you're wasting your time. Life is too short to put your self into knots. Just do the training when you have time and take on the challenge of the triathlon when it comes. Know you can leave if you want, but in most cases you're going to stay to play!