Yes, and to reduce the risk of bank erosion and to moored boats and riverside properties they must be adhered to.  The speed limit will depend on which river you are cruising but it ranges from 3mph to 6mph.  Please ensure that you pay particular attention to the speed limits, there are speed check areas on the Broads and the River Inspector is regularly patrolling in the Broads Authority launch.  There is also a Broads Beat fast response police patrol.