I did an Ironman last year, but it was probably not the best use of time and money as triathlon races (especially those sponsored by Ironman) are not inexpensive and end up being more like mini-vacations than weekend races. I enjoyed doing it for the sake of trying it and having a sense of accomplish at the end of the day.
If looking healthy is your primary goal, I think strength training + cardio is much more time efficient than cardio (like triathlons) alone. Now I'm focusing on surfing in the mornings when the conditions are good and lifting (mainly bench/squat/deadlift) otherwise. If you aren't familiar with these lifts, scheduling time with a trainer helps prevent you from missing workouts while ensuring you aren't doing yourself harm. Occasionally I'll play volleyball and I'm hoping to get back in climbing as well.
Playing team sports is also a great motivator for doing cardio. Its much easier to run when you're committed to doing it with your friends and letting them down can be worse than letting yourself down.
Also never drive if you can help it. If its less than 2 miles, walk. If its less than 5 miles, ride a bike. You'll save a ton of money in the process as well.
Aside from the above, plenty of rest (9+ hours a night) and eat healthy (sort of).