An underwater channel system is incised in the Holocene fjord basin sediments of Bute Inlet, British Columbia. High-resolution side-scan sonar swaths and seismic profiles reveal two channels within a zone of extensive rotational sliding on the slopes of a fjord-head delta. The channels coalesce into a single sinuous channel that extends 14 km downfjord on a 0.9° slope where it splits into two distributaries, which continue another 18 km, ending within stacked depositional lobes. Piston cores show sands in the channels and lobes in contrast to deep-water silty clays in the basin floor. The sea-floor features and sediment distributions result from active, highly mobile slide-generated sediment flows, which transport sands via the channels from the delta to the fjord basin.