After they were executed for their crimes, and instead of waking up in the afterlife, the eight found themselves on a ship that had anchored in the middle of the sea. The ship slipped into a whirlpool that took them to the shore of an island, where they saw horrors.

At this point, you have a premise but not yet a story. (At least by the logline)
To turn the premise into a story, you need a lead character, with a goal, and something standing in the way of that goal.
The premise sounds interesting.
Now it just needs an equally compelling lead character.