Charon the Ferryman is the entity charged with guiding the souls of the dead across the afterlife's river Styx. He fancied a day off, so he's persuaded his colleague Death (who normally handles the bit just before this) to mind the coracle for him.
It hasn't occurred to Death that, because he didn't get anyone to stand-in for him, the bereft of life are stuck at Death's Door unable to reach the riverbank. He assumes it's just a slow day, and is taking advantage of the lull to do a spot of fishing. Styx bream are delicious, you know.