Diss is a market town, civil parish and electoral ward in South Norfolk, England; it is near the boundary with Suffolk. It had a population of 7,572 in 2011. It lies in the valley of the River Waveney, round a mere covering 6 acres (2.4Â ha) and up to 18 feet (5.5Â m) deep, although there is another 51 feet (16Â m) of mud.