Breathe in and out through your mouth. Gradually, start varying the intensity, duration and depth of your breath. Focus on its sound. You can experiment with the different possibilities of sounding. Breathe in sometimes quietly and others more loudly; sometimes breathing in with a hiss, for example. Or, initiate the breathing out with a more explosive “p”. You can experiment with the different possibilities. What does the sound of your breath remind you of? How does it compare to the sound of waves as they break on the shore?
You can breathe into a microphone, if you have one. Notice how the sound is tranformed by the amplification.