Breathing out underwater: bubbles and the two-one rhythm
Almost every beginner's panic in the pool traces back to a habit learned on dry land: holding the breath the moment the face goes in. Trapped air makes the chest feel fuller and tighter, the head jerks up for air, and the body sinks with it. So the first real swimming lesson reverses that habit. Air leaves slowly while the face is in the water, and comes in through the mouth only once the mouth has cleared the surface.
The drill is simple and done standing in chest-deep water. The learner breathes in through the mouth, bends forward until the face is under, then lets the air out through the nose and mouth until a steady stream of bubbles appears. An easy rhythm to remember is two counts breathing out in the water and one count breathing in above it. Ten to twenty repetitions per round help the pattern move from conscious effort to habit. Well-fitting goggles keep the eyes open, and seeing the pool floor clearly calms nerves more than most people expect.
Most swimmers trip over the same pair of problems in the shallow end. The first is water up the nose, which happens when the exhale stops too early; the fix is to keep a thin stream of air going until the face is fully out. The second is gulping too much air, which leaves the chest stiff and over-full. A moderate breath in is plenty, because comfort in the water comes from a steady breath out.
When the bubbles flow evenly the whole time the face is under and the breath in feels relaxed, the breathing base is ready to carry into movement.