Cool!
We have an Aquabike/ Half Ironman series here in September. Basically the same distances you mentioned.
I was going to do it... but unfortunately I can't afford the entry fee. They are charging the Aquabike $175... the same price at someone doing the Half Ironman. Ugh.
Best of luck with doing it!
If you were a swimmer in H.S. you will get up to speed very quickly on the swimming. I trained 1 day a week for about 2-3 months for my 1.2 mile swim and completed it in about 35 minutes... even with piss-poor sighting.
You will do just great!
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"