Mistress Tess has one of the best bum's known to civilisation. Any slave given the privilige to struggle for air under it is truly honoured and will try as hard as they can to hold their breath and enjoy the position that they've been lucky enough to fin themselves in. The desire to breathe eventually gets them, but that's when Mistress Tess pushes this slave that little bit further, making them struggle and see stars, what a way to go though!