Some of the highest tides on this planet sweep into the Bay of Fundy twice every day, creating tidal rips and tidal bores, emptying and refilling harbours, making rivers run backwards, and nourishing incredible life on vast mud flats. The Bay of Fundy is like a giant bathtub sloshing 100 billion tons of tidal water back and forth, literally shaping the coastline of two Provinces and affecting all life along their shores. At Hall's Harbour, in New Brunswick, the tides must funnel into a narrow channel. With a time-lapse camera we see boats floating high against the wharf, and then sitting on the mud six hours later. And at the north end of the Bay of Fundy the Shubenacadie River reverses itself as a powerful tidal bore from the ocean marches up river at high tide. Around the shores of Grand Manan Island, fishermen use the tides to catch herring inside simple and traditional weirs. John and Janet Foster explore all of these phenomena, and witness the extraordinary mating rituals of the endangered Northern Right Whales - animals that depend on the rich ocean pastures created by the upwelling nutrients in Fundy's tides. And with help from a mud scientist they witness the mass flights of thousands of migrating shorebirds that come down from the arctic to feed and refuel on tiny shrimps in the tidal mud flats, before continuing non-stop to South America. Their flights are aerial ballets of precision turns and synchronous formation flying. Fundy's tides are a powerful biological engine, an irresistible force of nature.