The term "Water Caste" refers to a social group in the fictional universe of Dune, created by Frank Herbert. This group is primarily composed of individuals who manage and distribute water, a vital resource in the desert planet of Arrakis. The Water Caste plays a crucial role in the survival of the population, as water is scarce and highly valued. Members of the Water Caste are often seen as lower in status compared to the ruling elite, such as the Nobility and Fremen. Despite their lower social standing, they hold significant power due to their control over water resources, making them essential to the ecosystem and economy of Arrakis.