Your not gonna like what I have to say now BUT you have to be able to do the freestyle stroke... the forward crawl. It's true, it's true. It's really the fastest way to swim once you get decent at it. If your not good at swimming...take a few lessons. Having good technique will make things so much easier. You should understand if you know a little bit about how I trained...
Once upon a time, in a pool that wasn't so far, far away, I learned to swim. It was at the YMCA. I took lessons for about 3 years in elementary school. When I stopped with the lessons, I had progressed from a tadpole to a dolphin...I wasn't a shark or flying fish though. I was decent but didn't really care for swimming...my parents just wanted me to do something besides causing trouble.
Anyways, I never really swam for two decades until I started training for the swimming part of my triathlon. I thought it would be a piece of cake. You know, I was running good for the past two years, I figured my lung capacity from running and my much prior swimming training would carry me through easily...WRONG!!! When I first tried the forward crawl, freestyle stroke, I about died half-way through my first lap. I had to be able to swim a mile in a few months...what am I going to do? Hmmmm..... Well, I started doing many laps of the breaststroke, an easy stroke for me - kinda like my resting stroke...if needed I could do it tirelessly for an hour. I slowly worked in the freestyle. I would do 8 laps of the breaststroke and then 1 lap of freestyle then 8 and 1 again. I gradually was able to do get it to 2 laps of breaststroke then 1 lap of freestyle...it was not fun though...still very difficult. During this time, I always brought my head up to the left to breath after every stroke...not necessarily good. How am I to progress further?...I felt like I ran into a brick wall.
Well, one of the speakers at my mom and dads Nikken product roll-out was a triathlete. She had just done her first. She had a lot of tips. Relevant to swimming, she told me that it is very important to be able to breath on both sides. Some people could be splashing you on one side or waves can be coming at you on a particular side impeding your breathing...allowing you to get a mouthful of unpleasant tasting H2O. So being able to breath on both sides will benefit you.
To be able to breath on both sides, you need to learn the 'alternate breathing' technique. This is alternating the side you breath on, on every third stroke. Sounds cool? Absolutely not! This was the hardest part yet! It is the weirdest feeling trying to breath on the other side...like writing with your other hand. You must also learn to hold your breath for two strokes. Being that I could barely hold my breath for one stroke this proved very difficult. For about a month I felt like I was drowning but then the next time I went swimming I never noticed that I had to fight to hold my breath!!! I did it.
I then went back to swimming breaststroke for 6 laps and then the alternate breathing freestyle for one lap. Before race day I had significantly improved. I was doing two laps of the freestyle (alternate breathing) to one lap of breaststroke (my rest stroke). I was doing this without too much effort. I had finally stopped gasping too.
What did all this extremely horrible work do for me? Well, doing the alternate breathing freestyle stroke allowed me to be able to concentrate on my swimming for two whole strokes - giving me speed and power. Think about it, every time you go up to breath, you lose 'focus', your stroke breaks down. This improved freestyle stroke also dramatically improved my speed. My lung capacity also improved greatly. Although it is good to know the alternate breathing style, you don't really need it for racing unless its wavy or splashy to one side. If you have problems getting enough air, it's better to breath every stroke for optimal oxygen intake so you're not as tired on the bike and run.
Now I love swimming. It gives me that runners high afterward. It's a great total body workout. I hope that you really give swimming a chance...it will be hard work in the beginning but all of the sudden you will be doing it effortlessly. I feel it's the best exercise for you.