As technical as the sport of swimming can be, it is tough to narrow down the answer to the often-asked question, "what should I concentrate on?" So, I came up with a "top ten" list of steps to improving your swim for a triathlon. These aren't necessarily in any order but should go a long way in helping you achieve your goals, whether you are a beginner or trying to go pro.
1. Hand Entry.
Slice your hand into the water right about at your goggle line, and drive it forward. Many swimmers attempt to get as much "air time" as possible by reaching the hand out before entering into the water, but it is actually more efficient to go through the water with your hand as you rotate from one side to the other.
2. Head Position.
Keep looking straight down when swimming freestyle. It's important to keep your head down with only a small part of the back of your head out of the water. Also, as you rotate through the water, try not to move your head with the rest of your body rotation.
In freestyle, your hands should pull all the way back past your hips. The last part of the stroke before recovery (arms coming out of the water) should be an acceleration behind you, and not up out of the water.
Try minimizing your kick as you train for swimming. Most people will kick extra hard to make up for lack of balance in the water. Minimizing your kick will allow you to improve your balance, as well as conserve energy.
5. Training Intensity.
The best way to measure your training intensity is to count your heart rate immediately after each swim. You can estimate your heart rate by counting your pulse rate for six seconds immediately after each swim. Add a zero to this count, and you will have your approximate exercise heart rate per minute.
6. Master's Swimming.
Move to a slower lane to work on stroke improvement. If you belong to a masters team, don't feel that you always need to keep up with your lane-mates at every workout. Masters teams typically have many people with many different swimming goals. It's important to do your own thing! Remember that technique comes before all else and if this means swallowing a little pride to make improvements, just think of how much faster you will be for this in the long run.
7. Habit: Keep your arm from crossing over.
One of the most common bad habits I see in swimmers is the arm crossing over to the opposite side on the pull. Breathing on your left side results in your right arm crossing over, breathing on your left side results in your right arm crossing. Often times this happens when one goes to breath, but sometimes it's caused just from over-rotating. To avoid this, make sure your head isn't moving with the rest of your body, and try to pull more in a straight line (still bending the elbow) and ending the pull on the same side you started (i.e. right-hand slices into the water, pulls back and hand ends up near right hip).
8. Keep the Feel.
If swimming is your toughest sport, it is important to "keep the feel" for the water, and get in the water at least every other day (no, showers and baths don't count!) This way, your body maintains its kinesthetic awareness of being balanced in the water.
9. Work Those Lungs.
Mix in some hypoxic training sets into your workouts. For example, do a set of 4x100's breathing every 3-5-7-9 strokes by 25, with 15 seconds rest in between each 100. Your lungs will thank you for it towards the end of the swim part of your race!
10. Work Your Weakness.
In the sport of triathlon, most coaches agree that you should spend the most time working on your weakest of the three sports. For many of you, this will be swimming! Within swimming, the same concept applies. Spend the most time working on the weakest part of your stroke. If balancing on your side is an issue, do some kicking drills on your side. If moving your head is a problem, focus on head position most of the time.
Whatever it is, you will gain the most by spending your pool time improving on that weakness.