Reversing Falls, Coastal waterfall in Saint John, Canada

Reversing Falls is a series of rapids on the Saint John River in Saint John, New Brunswick, where the river passes through a narrow gorge into the Bay of Fundy. A steel arch bridge with green trusses and stone piers crosses the gorge downstream. Underwater ledges roil the water in either direction, creating a navigation hazard despite the depth.

The Wolastoqiyik people lived at this river mouth for thousands of years and used the changing tides for navigation and fishing. European settlers reached the area in the 1600s and built a port town around the natural passage.

Local names for the rapids reflect the tide-driven movement that shapes daily routines of fishermen and boat operators who time their crossings carefully. Visitors watching from shore can see how the current shifts direction, sometimes creating smooth channels and other times forming turbulent white water.

Fallsview Park occupies the former foundry grounds on the east side of the gorge, and the road bridge and the 1922 railway bridge cross just downstream of the rapids. Boats enter or leave the river only at slack tide, when the current pauses between directions. The flow reverses over a 12.5-hour cycle, so the water changes direction roughly every six hours.

The Bay of Fundy holds the world's highest tides, causing the river to reverse direction every 12.4 hours and form a 4.4-meter cascade. At low tide the water flows normally toward the ocean, while at high tide the rising seawater pushes the river backward and creates a reverse current.