Rice trunks like the one pictured below, from an 1867 issue of Harper's Weekly, were raised and lowered to control the flow of water.
From Harper's Weekly, January 7, 1867. Courtesy of the Hargrett Rare Book and Manuscript Library, University of Georgia, Athens, Ga.
The fresh water inundated the rice fields at high tide and drained them at low tide, days or weeks later, killing weeds, protecting the seed from birds and the sun, and watering the rice plants.
For enslaved laborers on these Lowcountry rice plantations, the work was difficult and dangerous, involving exposure to disease, extreme heat and cold, and often working waist-deep in mud.