Swimming a longer training program or competition is not so much a matter of how well trained your muscles are. Yes, it is important to build up muscles and strength but the crucial thing for speed and endurance in the water, is how you breathe. In the same way as you learn your swim techniques, you have to learn how to get a good breath control. It doesn't matter whether you are a beginner or an experienced swimmer, learning & practicing proper breathing technique is the major challenge on your way to become a good and fast swimmer.
If you want to swim fast, you should learn freestyle swimming. It is the only swim technique that combines speed and endurance, if done correctly. Practicing freestyle starts with learning how to breathe while your head is in the water. But keeping the head down in the water is a big challenge for many people who have just taken up freestyle swimming. Everyone has a different level of water confidence and this level may even change depending on where you swim.
So, the first step as a beginner, is to improve your water confidence; meaning to get more relaxed and comfortable with the element water. This can be done by practicing a few basic exercises in the water. It is advisable to wear swimming goggles while doing the exercises to keep the water out of your eyes and ensure good visibility.
keep your head in the water
The first part of the exercise is very simple and aims to make you comfortable putting your head under water and breathe into the water. For that you hold yourself in the water on the pool edge, facing the wall, with both hands while your arms are straight in front of you. Now you bring your body in the horizontal position, parallel to the water surface. To hold this position while your head is above the water level, you may flutter kick slightly with your legs. Take a breath, then put your head in the water between your arms and look straight down to the bottom of the pool. Now very slowly breathe out. You will notice that it is suddenly much easier to keep the horizontal position while your head is in the water. Your neck and back muscles are relaxing and your hips and legs go up to the surface. You may repeat this part a couple of times. Head out - breathe in; head down - breathe out.
you cannot drown
The human body is composed of 60% water and has a slightly higher density than water. This means, we would sink down in the water if there wouldn't be our lungs. By filling our lungs with air, we decrease our bodies density to slightly less than the density of water. The rest is physics, in particular the "axiom of Archimedes" that ensures that the water will lift your body up to the surface. The next exercise is to make you feel comfortable and familiar with your own buoyancy. In the water, bring your body in a horizontal position by turning on your back. Your face is looking straight up to the ceiling of the swimming hall. The main part of your head is under water, only your face is above the water surface. Spread your outstretched arms 90 degrees away from you body and open your legs a little. Take and hold a deep breath and stop moving your limbs. You will realise that you are floating. The moment you breathe out the floating effect will vanish. You breathe in, buoyancy will come back. This is a perfect exercise to understand one important thing: You cannot drown.
gliding through the water
This exercise aims to make you glide in horizontal position through the water. It is split into two parts. First turn your back towards the wall of the pool. Extend your arms in front of you keeping them below the water surface. Take a deep breath and put your head in the water between your arms, face down. Draw your legs up by bending your knees, extend your legs backwards and push yourself off the pool wall. Stretch out your body, make yourself as long as possible, and glide through the water as far as you can. When the forward momentum stops, breathe out into the water and take your head up. Repeat this part a few times but try each time to extend the glide a little further. Second part. As in the first part you push yourself off the pool wall and glide through the water. The moment you lose momentum, you start flutter kicking with your legs without taking your head out of the water. When you can't hold your breath anymore, you take one arm from the front and stroke down to your hip and rotate your upper body slightly. Keeping your head in the water, you turn your face sideward out of the water and breathe in. Your legs are still kicking and you glide a little more through the water without changing your position. Repeat this exercise until you feel well balanced and comfortable keeping your head in the water.
Practicing these few exercises will make you gain water confidence. You will begin to trust and love the element water, instead of fighting it. Step by step you will enjoy the feeling of being supported by the water and become one with it. Don't be impatient and take your time with the exercises. Once you have improved your water confidence; the next step is to learn the basics of freestyle swim technique and develop effective breathing habits. So, dive in and let the water embrace you and most of all "keep your head down".