Swimming is 90% skill. If you are a weak swimmer then your number one expense for race preparation should be paying for swimming lessons from a good coach. So many triathletes are willing to spend thousands on faster bikes and nothing on good swim coaching.
You have a choice when it comes to swimming. You can get out of the water tired and drained or you can get out fresh and ready to ride. The difference is in your swim technique. Good technique allows you to slide through the water with less effort. A swimmer with bad technique overcomes this deficit by expending much more energy and usually swimming slower.
For your first race, you just want to make sure you can swim the distance. If you get out tired, you will take it easier on the bike until you can go faster. But if you are able, get some personalized swim lessons from a good coach.
You may hear people talk about joining a Masters swimming team. This is fine if that’s all you have, but Masters swimming is all about go go go and there is little patience for slow unskilled swimmers. If there is a Masters swim near you, find out who the coach is and see if you can book a few personal swim lessons. You need a coach who is looking at your swim and suggesting drills and technique changes often. A go go go coach that is barking out swim orders to twenty swimmers will get you stronger but wont help at all with your swimming.
When I joined my first triathlon club, one of our first swims was to figure out how fast each athlete was so we could be assigned lanes based on our speed. Well, I have a big problem when I am put side by side with other athletes and told to race. Even worse is when we will then be placed in lanes according to our speed. My problem is that I go all out. I may be dead at the end of it, but oh well. So we did this little test and I was placed over with the fast athletes with a coach that just barked orders and never looked at anyone’s swim.
I swam with the fast swimmers for a while and noticed that the slower athletes were actually getting more coaching on the other side of the pool. So I snuck over with the slower swimmers. I did that because I wanted to learn how to swim well. I knew I could go fast for a short time. But I also knew that speed wouldn’t last over a long swim.
My point in telling you all this is that you need to advocate for your own training. You need to find the coach who will help you with your swimming technique and not the coach who will tell you to go go go. Get your technique down first, then you can go fast for a long distance.
The best place I have found for learning how to work on your swim technique is Swim Smooth (http://www.swimsmooth.com). They have animations showing you the proper technique, apps, and articles every week on good technique. I could go on and on but it would never be as good as what you will find at Swim Smooth. Go there, sign up for their newsletter and you will get valuable lessons sent to you every week.