The Tau Water Caste is made up of merchants, diplomats, and administrators. They are responsible for maintaining effective interaction between the castes, as well as communicating with and supervising the integration of alien species into the Tau Empire. Members of the Water Caste tend to be taller and more slender than other Tau, and their features are softer and more expressive. Water Caste Tau will frequently adopt the mannerisms and other cultural habits of the intelligent races they deal with, although this is often done to promote communication with these other species.
Water Caste members are bureaucrats, politicians, negotiators and administrators. They are the merchants and diplomats of the Tau Empire, moving in and around the other castes to ensure that Tau society functions smoothly, always in the service of the Greater Good. Water Caste members often accompany Tau expeditionary forces to negotiate safe conduct through alien star systems and smooth the passage of Tau merchants and colonists. Servants of the Imperium of Man should be aware that these Tau are exceptionally skilled at manipulating weak-willed individuals and every remark addressed to a member of the Water Caste must be carefully considered and phrased to prevent any sensitive information from being divulged.
- Codex: Tau Empire (7th Edition) (Digital Edition), "The Castes"
- Codex: Tau Empire (6th Edition), pp. 7-12
- Codex: Tau Empire (5th Edition)
- Codex: Tau Empire (4th Edition), pg. 9
- Codex: Tau (3rd Edition)