What should I do if I sink under the back row and fill it with bubbles?

Standing posture, arms straight across the back of the head, hips clamped and stretched upward, legs together, stand on tiptoe, and feel the whole person stretching upward. Stick to it for one minute and do more groups to help maintain your position in the water.

Sit on the ground, put your arms straight behind your head, put your upper and lower back, keep your feet off the ground, and keep your toes straight 1 min. Kick quickly. You can also put your hands behind your body, keep your feet off the ground, straighten your toes and do kicking. Kick up and down at your fastest frequency for one minute, and then continue to increase the persistence time. It is best to have 15 minutes of practice every day.

When your legs fight, your ass gets up, and the problem of paddling can basically be solved.