20 minutes, 111 breaths, just for you. A long out-breath tells your body it's allowed to relax; how that feels for you, you'll notice for yourself after a few sessions. Sit or lie down and breathe along with the light and the waves.
When the light grows and turns golden, breathe in through your nose. When it gets smaller and cooler, breathe out slowly. When you hear the rush of a wave, breathe out. That way it works with your eyes closed too.
The pace slows down a little on its own as you go, and your out-breath always stays longer than your in-breath. Too fast or too slow? Just breathe at your own pace and listen.