Eight places, in a fixed order
A spring is where water begins and the sea is where it ends, so the order can never drift: the Sleepy Forest, the Sleepy Springs, the Snoozy Stream, the Sleepy Waterfall, the Sleepy Lake, the Starlit Shore, and — heard, never arrived at — the Sleepy Sea. Every place goes to sleep in its own way, and the stream stops babbling sound first, then surface.
You choose how far you are going before you set off, and then nobody has to decide anything else. Choosing is thinking, and thinking is the enemy at bedtime. The whole route is here.
It does not matter whether you hear the end
Each story is told slowly, with the same phrases returning again and again, and it ends on a held sleeping frame rather than an ending. If your child is asleep by the waterfall, the story has done its job better than if they heard it all.