What is "watermasters"

Usage examples of "watermasters".

She looked down the shadowy line of Fremen, saw Stilgar with Paul standing beside him and the watermasters emptying their load into the pool through a flowmeter.

Then one of the watermasters came forward and pressed the tip of the tube into Margot's mouth, collecting the drop of transformed liquid, which he then dipped into the contents of the sack.

Beside her, the ancient woman released her grip on the second tube, and other watermasters spread the transformed poison from one container to another like firestarters touching flaming brands to a field of dry grass.