You may desire to join in the fun of underwater swimming yet not be able to do it without holding your nose. Learning breath control starts with relaxing in the water, becoming comfortable splashing water on your face and submerging. If you are already comfortable this may only take a few sessions. If not, allow yourself four to six weeks or whatever it takes.
Start in shallow water or in the bathtub. Cup your hands and hold them chest high. Keep your face and hands out of the water. Inhale through your mouth, close your lips and exhale through your nose. Feel the exhaled breath in your cupped hands. Now fill your cupped hands with water. Inhale through your mouth and close your lips. Lower your nose into the water in your hands and exhale for five seconds. Lift your head and repeat until you think it is easy. Increase your exhalation time to 10 seconds.
Lower your cupped hands into the water, but allow your thumbs to remain on the surface. Inhale and lower your nose to the water in your hands and blow bubbles for 10 seconds. Continue until this is easy. Submerge your cupped hands two inches and do it again. Take your hands away and do it again. Continue until it is easy. These seem like baby steps, but if you rush and allow panic at any stage, you have gone too fast.
Start with a partner in the shallow end of the pool. Hold the side of the wall. Inhale through your mouth, submerge your head and blow bubbles out your nose for 10 seconds. Come up and inhale through your mouth, submerge and blow nose bubbles 10 more seconds. Set a goal of three consecutive, 10-second breaths of submerged nose blowing. Increase this one at a time until you can take 10 consecutive 10-second breaths. Practice until you have completely mastered this technique. It might take one session or a few weeks.
Use the breath control skill to explore. Release the wall. With your feet on the bottom of the pool, inhale through your mouth, submerge and exhale 10 seconds of nose bubbles. Stand and bring your head out into the air and inhale through your mouth. Submerge and repeat until it is easy. Next, submerge and retrieve an object. If you can control your breath to do that, all you need is more practice.
Always swim where there are lifeguards on duty. Swim with a partner.