Starting into to this. Is this plan way off the mark or something to work towards.

Hi all.
I've just decided to focus on completing a HIM this coming Sept '16.. I've done a couple of half marathons and a sprint tri in the past as well as playing a-lot of competitive team sports so the running aspect doesn't daunt me. That said, like most, the swimming is my weak link.

So here's where I'm at. - I've joined a masters swim program 3 weeks back.. with the steady focus of moving up to a consistent 2000 yrd swim with no breaks in the pool. Working on technique and stamina etc. I was a self thought swimmer from when I was kid.. no technique and never done laps so basically I was a slow drowner as opposed to a swimmer. 3 weeks into the training sessions, I'm finally up to a 1500 yrds (broken) 1 hr session with the basics of swimming stroke kicking in.

My goal for now is to focus totally on the swimming from now until June. 5 days out of 7 - 1 hour sessions. Then come May start adding the running and cycling into the daily mix. The end goal on the swimming is to be able to hit a comfortable 2500 to 3000 yrd session, just so I know I can swim the open water safely. [ I kid you not, 3 weeks ago I could barely do 2 lengths in the pool without coughing up my lungs.]

On day 6 and the odd day in between I knock out a 45 min, 10 / 11 mile mtn bike cycle which I like, as it forces me to work just to keep up speed, but more so to give me some saddle time until I get a road bike - something is better then nothing. Day 7 a light 3 to 6 mile run.. nothing strenuous.

Come June my logic is to start working to one of the many good plans out there - yet to be fully decided which one - lots of reading yet, but thinking one where I get 2 activities / bricks in on a daily basis 5 out of 7 days. With maybe a Wed rest and a Sun rest. Light on the start of the week, building up to heavier end of the week .. and increase the load week by week with a tail off 10 to 14 days out from the race in Sept - I'm thinking of doing the Santa Cruz 70.2 come Sept. Not to mention add in food / nutrition consideration along the way. And actually get on a road bike consistently versus the mtn bike right now.

So here's my question - - Is this approach reasonable to work up to hitting the 70.2 safely and comfortably by Sept. Yes each person is unique, but is there anything alarming about taking this approach.. is combined training(swim.bike.run) from May a good target? and will 6 months be enough to train ?

Tks everyone and very interested in your thoughts etc

For reference I'm 36yr M, 5ft,10, 210 lbs, solid mass. Can run a steady 7.5 min mile on the treadmill.

S.