If you're like most triathletes, practicing your swim breathing technique never happens.
This is strange when you consider that it represents the most inefficient part of the stroke cycle! Yet practicing how to breathe properly during your swim training is every bit as important as other technical swimming drills in order to learn to stay relaxed and conserve valuable energy you'll need later in the race.
If you lift your head out of the water, over rotate, or even worse just hold your breath until you come up gasping for air then all you're doing is spiking your heart rate and slamming on the brakes every time you breathe. That's why you need to practice how to breathe first in your swim training until efficient swim breathing becomes automatic: Energy management during the swim hinges on smooth, relaxed breathing.
Swimming requires full body coordination during your stroke cycle along with your breathing. To improve your swim breathing use the same stroke drills you normally would. The only difference is you start with a FOCUS on your breathing. Once you get comfortable with your breathing during the drill then you'll be ready to maximize the benefits of that particular drill because you'll be more relaxed and aware.
Here are two examples to get you started. Remember, start slow:
Single Arm Drills With Non-Swimming Arm in Front
Start with both arms extended in front of you. On the first 25 yards keep your right arm extended and only use your left arm to take strokes breathing every 2nd stroke on your left side. On the second 25 yards keep your left arm extended and use your right arm to take strokes breathing every 2nd stroke on your right side. Focus on fully exhaling underwater and then only rolling as far as necessary to get a deep breath.