Located in Canada, between the provinces of Nova Scotia and Brunswick, sits the Bay of Fundy, home to the world largest tidal variations. While the earth's average hight variation in sea level from tides is three feet, the water level near Wolfville, in Nova Scotia's Minas Basin can be as much as 53 feet (16 meters) higher than at low tide.
Tides along the Atlantic coast are basically semi-diurnal, meaning there are two significant high tides every 24 hours. Along the Atlantic coast side of Nova Scotia Atlantic coast, outside of the Bay of Fundy, the tidal range is from four to eight feet (1½-2½meters) and without much variation in the time of the high and low tides.
So, why is there such a large variation in the tide inside of the Bay of Fundy verses outside? It is because of the funnel shape and depth of the bay...and a little physics.
Liquid in a tank, or in this case a basin, will flow back and forth in a characteristic "oscillation" period and, if conditions are right, will rhythmically slosh back and forth. In essence, a standing wave develops. The natural period of oscillation in the Bay of Fundy is approximately 12 hours which is about the same length of time for one tidal oscillation (a high/low tide cycle). This coinciding of the tide cycle and the oscillation period of the bay result in the much larger tidal ranges observed in the bay verse what occurs outside of the bay.
The huge volume of tidal water flowing through of the bay fours times daily has created some unique features such as the "Old Sow" whirlpool (the largest whirlpool in the Western Hemisphere), the "Reversing Falls" (series of rapids on the Saint John River that reverse direction with each flood and ebb tide) and the Hopewell Rocks (rocky islands at high tide and a place where you can walk the beach and explore these formations along with the many caves cut into the cliff walls at low tide).