You sink into the mud, and soon the water is up to your neck, then your mouth, then your nose. You drown and die.

Return to the beginning of the story.

How many story branches end in a quick death? 

The story leads to six endings. Two are violent deaths and three are peaceful. One peaceful ending escapes and one cycles back into the story and meta-story.

It seens like returning to the beginning of the story is more like being reborn in a game, so the propulsion of narrative energy is lost. It stops being a story and turns into a puzzle.

A narration can be both a story and a puzzle. In some games you are reborn at the beginning and in some you don't have to start over. In this case the story is small enough that going to the beginning is possible. Readers can always use the Back button if they want to go just one step back.

Shouldn't you have pointed that out at the beginning?

It's always an issue how much context to supply. You have to presuppose some things. Or leave them for the reader to figure out.

Such as how to read our conversations between two voices.