Choose your coastline
The published Sleepi collection includes ocean and calm beach sounds alongside rivers, lakes and waterfalls. Listen to a short sample and choose the character you prefer: the repeating motion of waves is different from the more continuous flow of a river.
Give the waves some space
Try the ocean track alone before adding another sound. If you want a layered atmosphere, add a quiet nature track and adjust each volume separately in the mixer. Too many strong layers can hide the detail you liked in the first place.
Make it fit your evening
Set the sleep timer if you want playback to end, or use background playback while you put your phone aside. AirPlay lets you choose a compatible output device. Recheck volume after switching outputs, and keep it comfortable. Ocean sounds are an atmosphere to enjoy, not a promise of a particular sleep result.