Water is party to all things, dear reader. While all Earth-dwelling embodied lifeforms have their own characteristics, goals, needs, and expectations of their environments, water is a common necessity they all share. Without proper hydration, the brain's receptors stop interpreting and correlating information and general organ failure occurs, plants are unable to photosynthesize, and moisture continues to evaporate from the body at a rather high rate.
While each species has its own unique traits and properties, all share an inherent hardiness in dry, arid conditions. However, because they evolved to exist in regions largely devoid of water for the majority of the year, they are highly suceptable to over-watering and potential rotting--either from fungus or from being waterlogged.