This is the most challenging roguelike I've ever played.  Initial freediving passes are rewarded by an undisturbed silt layer.  It takes several rotations of an area just to map out a strategy of how to proceed.   The mechanics of the life line just works beautifully.  Even quick jaunts down well placed lines are rewarding when you don't have a lot of time.  Every death is truly a major setback.  Kudos to the developer on this one.