The tidal range in the Bay of Fundy is about 52 ft. (The average tidal range worldwide is about 3.3 ft.) Some tides are higher than others, depending on the position of the moon, the sun, and atmospheric conditions. Tides are semidiurnal, meaning they have two highs and two lows each day, with about six hours and 13 minutes between each high and low tide.
Because of tidal resonance in the funnel-shaped bay, the tides that flow through the channel are very powerful. In one 12-hour tidal cycle, about 100 billion t (110 billion short tons) of water flows in and out of the bay, which is twice as much as the combined total flow of all the rivers of the world over the same period. The Annapolis Royal Generating Station, a 20 MW tidal power station on the Annapolis River upstream of Annapolis Royal, was one of the few tidal generating stations in the world, and the only one in North America.
Most of the rivers have a tidal bore, a wave front of the incoming tide that "bores" its way up a river against its normal flow. Notable ones include those on the Petticodiac, Maccan, St. Croix, and Kennetcook rivers. Before the construction of a causeway in 1968 and subsequent siltation of the river, the Petitcodiac River had one of the world's largest tidal bores, up to 6.6 ft high. Since the opening of the causeway gates in 2010, the bore has been coming back, and in 2013 surfers rode it a record-breaking 18 mi.
Other phenomena include the Reversing Falls near the mouth of the Saint John River, a rip tide at Cape Enrage, and the Old Sow whirlpool at Passamaquoddy Bay.