Seymour Narrows is a 5 km (3.1 mi) section of the Discovery Passage in British Columbia known for strong tidal currents. Discovery Passage lies between Vancouver Island at Menzies Bay, British Columbia and Quadra Island except at its northern end where the eastern shoreline is Sonora Island. The section known as Seymour Narrows begins about 18 km (11 mi) from the south end of Discovery Passage where it enters the Georgia Strait near Campbell River. For most of the length of the narrows, the channel is about 750 m wide.