Cool! Check back in and let us know how it works out.
Make sure you aren’t trying to swim faster than you are really able. You shouldn’t be breathing heavily. You should be doing a slow enough swim that you can breath slowly and evenly. Don’t panic and pace yourself.
Also see if you can have someone evaluate your stroke for you so they can give you pointers. I love swimming but had to give it up after only 6 weeks because I pushed myself too quickly. I went from doing nothing to swimming a mile in that 6 wks and gave myself tendinitis in the shoulder. Take it easy and don’t push too hard to fast.
Cinnamon, I’m in the same boat as you, and on Monday I start with the swimming as well. I wish us both luck!
You might want to think about joining a Masters team. I know team can sound like it’s something only competitive swimmers do, but in this case it’s just a group of people who swim together. This will give you a coach to swim with and have them help you out with your stroke and other fitness items you may want to learn about. I’ve been with my team for the last 9 years, and I’ve swam with lots of others and I’ve yet to find one team that isn’t very accepting of new people and people who don’t swim very well. The people in the faster lanes aren’t going to be paying attention to you at all while they swim.
As for the breathing, yes you have to learn to get the air out before you turn to pull air in. Also you don’t want to be lifting your head, you want to rotate your entire body on it’s side while you swim. Then you can turn your head a bit more and breath. As one arm is out of the water you want to be turned to that side. You don’t want to be lifting your head as this will give you an uneven stroke and possibly cause shoulder problems.
I went this morning! Honestly, the biggest challenge may simply be social/psychological. Being heavy makes one self-conscious in a bathing suit regardless, and on top of that I was feeling unfamiliar with the culture of swimming, so to speak. I had to share a lane and I just felt like I was slow, awkward, and in the other person’s way. This is all irrational - I followed the rules, stayed on my side, etc. But try telling that to my brain’s emotional centers!
So, my point is I’m giving myself extra props for getting over all that and doing it anyway.
As for the actual mechanics, I think maybe I can’t swim crawl slowly enough to stay within my limits right now, if that makes sense. I warmed up with one length of freestyle, and was already huffing and puffing. So I did breast stroke and side stroke the rest of the time, which was easier to slow down, and also made it easier to keep an eye out for my lane partner.
I did concentrate on blowing out all the air I could while my face was in the water, and it did help.
When my shoulders started to feel tired, I just goofed around with some water aerobics moves in the unoccupied deep end, so I kept my heart rate up for 30 minutes. I am aiming to do this three times a week, switching off with Pilates and yoga on the other days. I felt like I did get a good workout, and I’m looking forward to improving as I go.
I popped in to suggest breast-stroke (get your mind out of the gutter, you perverts!) for exactly the same reason. It’s the only stroke I do when I’m trying to swim laps - crawl gets me winded far too soon - like after about 10 feet - while I can do the less aerobic strokes for much longer.
I would think a snorkel would require a bit too much concentration, especially doing the crawl, and has the risk of accidentally splashing water into the tube… or forgetting to clamp your teeth down… resulting in a lungful of water. Blech.
Total Immersion. There are books and videos (obviously, not much help when you are in the pool). You may be able to get them out of a library, and there is stuff online about the techniques.
This is a system that teaches you how to swim, or improve your stroke, by getting in synch with the water, sort of. It’s been awhile since I read the book, so I’m probably not explaining well, but it’s a good way to ease yourself into swimming.
I got into this when I saw a class at the Y where I swim. I tried to eavesdrop, because it looked very effective–then I got the book (from the library, which is why I can’t quote it).
I know no one is in to using “props” while trying to learn to swim, but when started swimming for exercise my only goal was exercise not being a top-form lap swimmer. Basically I was in the pool for an hour or 90 minutes to get my body moving and my heart rate up. Like I said, I am a fine swimmer so I didn’t have to try to learn to swim while I was trying to exercise, but if I just needed an excuse to get my ass moving in the pool, I don’t see what harm a kickboard would do.
Cinnamon, here’s some advice about feeling self-conscious in the pool: all the snarky fit people (that is, not all fit people just the ones who are snarky) say that fat people are lazy and need to exercise, so you are there to exercise and they can STFU. I bet they really don’t care, tho, as long as you obey the rules the best you can.
Also, the way I see it is that it’s no secret that I am fat when I am fully-clothed, so it should be no shocker to anyone to see me being fat in a swimsuit. No one is looking at me saying “oh I bet she has some stunning legs under those size 26 jeans!” Being a fat person in the pool is just no different than being a fat person on land.
Lastly, I really like going to the pool because I am blind as a bat without my glasses, and completely deaf to the world when I have my iPod*. If anyone is actually saying anything nasty about me, I’ve never been able to hear or see it 
Anyway, seems like you’re off to a good start. Keep going!
*Don’t worry, y’all. I am able to keep an eye out for other swimmers, hear lifeguard whistles and always check to see if there’s someone waiting to get into my lane.
A lot of great advice already, yet I must post because swimming is such good exercise. First I will add to the chorus of “get in there and do it.” I would also avoid using a snorkel. Snorkels are good when you want to stare at stuff under water but kind of a bother for swimming laps.
There will be people at the pool who just don’t understand what it means to be out of shape (like my children) and who may make comments or otherwise be mean. They are just ignorant. Please, please don’t let them keep you away from the pool. There is no better place for an overweight person to exercise.
Thanks, guys. I imagine most of the people at the pool are just focused on their own workout (or worrying what everyone is thinking of them), and not even noticing me much, but you know how it is. Luckily, I’ve gotten so fat, I’ve actually gone past a lot of the embarrassment about getting in a swimsuit. As **ZipperJJ ** said, it’s not like it’s a big secret I’m fat. No “slimsuit” or correct use of stripes is going to make me look much better. That leaves hiding at home or just dealing with it. Since I would never deny my kids their fun at the pool because I feel too fat, I’ve learned to just deal with it. Mostly. 
Oh, and I did look and find my YMCA has “stroke clinic” every few weeks, so I might look into that. No masters class, but if I really wanted that, I could travel a bit and find one.
Imagine having a skin condition covering half of your body while at the pool! I was mortified when I began swimming, but I ended up loving it - it almost feels defiant to be so exposed. I swam competitively until graduating high school and later coached a club, and lots of the advice is good so far - definitely take it slow so you don’t give up on it. It’s great exercise!
I have specific snorkel recommendation for you here.
You can shop around to find a cheaper one, but what you want is a “front snorkel”. Side snorkels get in the way of your freestyle (front crawl) arm motions. I’ve used front snorkels on and off to try and perfect my technique; it’s a great help to your stroke to not worry about rotating to breathe. I believe freestyle burns more calories than breastroke does, so if you’re doing it for health, I’d encourage freestyle.
And try the stroke clinic, especially if it’s free. Peruse craigslist, you may find some swimming lesson offers from the local college. If not, go to the local college pool and post a flyer there - you can find really cheap swim lessons (from people like me ;))
Yes I can almost guarantee that most other people there don’t care. Unless you happen to get in their lane when you shouldn’t be.
BTW it’s not Masters classes, it is a team, so everyone is there at the same time and they’ve reserved the pool to swim in. This way they will help you find the right lane to swim in. It looks like there is one in Cary, NC.
There’s also a few pages on getting started.