In one sentence, describe what the following article is about:

To get comfortable going underwater without holding your nose, it helps to practice in a shallow body of water. You can use the shallow end of a pool, a bathtub, or even fill a sink full of water to practice. A quiet part of a pool or a shallow pool designed for children can help make you feel more at ease in the water. To keep water from getting into your nose, you have to learn how to control the flow of air out of your nostrils. Practice by cupping your hands, placing your nose into your cupped hands, taking a breath, and exhaling through your nose into your hands so you can feel the air. Try exhaling for 10-second increments 2-3 times. Once you've gotten used to controlling the flow of air out of your nose by exhaling into your hands, you can try it out in the water. Lower your cupped hands in the water until they form a bowl filled with water. Then, take a breath, lower your face again into your hands, and exhale through your nose so you can feel the bubbles in your hands. Repeat the process until you feel comfortable putting your nose underwater. Exhale for about 10 seconds at first, then try to go for about 15 or 20 seconds to push your comfort zone. After you've gotten a little more comfortable submerging your nose in the water, lower your cupped hands a little deeper. Then, take another breath, submerge your face into your hands, and breathe out through your nose. Notice if you find yourself getting more comfortable in the water. Great job! Do this exercise a few times and try exhaling for longer and longer increments. If you feel confident enough, try putting your head under the water without your hands. Take a big breath and stick your head underwater, then blow out air through your nose. Exhale for longer increments each time you submerge your head Keep a small amount of air held in your nose to keep water from getting in. If you can hold your head underwater without exhaling through your nose, you're basically swimming! When you feel ready, take a big breath and go underwater. Try to not exhale through your nose and hold your head under the water for 10 seconds. Try to push yourself to hold your head under the water for longer and longer periods. If you feel really confident, try swimming around a little bit with your head underwater.

Summary:
Use a shallow pool or bathtub to practice. Cup your hands and exhale into them through your nose. Put your hands in the water and exhale through your nose. Move your hands 2 inches (5.1cm) deeper into the water and exhale. Put your whole head underwater and exhale through your nose. Hold your head underwater without exhaling for 10 seconds.