The surging Bay of Fundy tides, the highest in the world, cause the Moncton Tidal Bore to occur twice daily. The higher waters in the Bay cause the water in the Petitcodiac River to roll back upstream in one wave, which can range in height from 3 to 60 cm. Just as spectacular is the rapid and dramatic change in the river itself. At low tide the muddy river bottom is often visible, but within an hour of the arrival of the Bore, the water level rises some 7.5 metres (25') to fill the river to its banks.