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Almost half the world’s population lives in coastal areas. But to most of us the rules that govern the rise and fall of the tide are a complete mystery.

Knowing when and how much the tide will rise and fall each day is crucial to many people, from ship’s pilots and marine biologists to surfers and boat operators. Miscalculating the size and time of the tide can have expensive, even deadly consequences. Our quest to understand the tide takes us around Ireland, the UK and across the globe.

We begin in Canada’s Bay of Fundy, where tourists flock to see one of the year’s highest tides. Guide Kevin Snair shows them how the shape of the bay together with tidal resonance and the alignment of the Earth, moon and sun combine to produce the world’s largest tidal range.

Champion surfer Dr Easkey Britton showcases her skills on the waves off the Donegal coast. Growing up in a surfing family in Rossnowlagh, she quickly learned the importance of understanding the tide to find the best waves and surf them safely. Today as an expert in environment and society, she is fascinated by our innate connection to the sea.

The tide produces many natural wonders, from whirlpools to tidal bores. On the River Severn, the potent tidal bore can give surfers an exhilarating ride of more than 15 kilometres.

In China the relationship between the moon and the seasons is celebrated on the banks of the Qiantang River during the Mid-Autumn Festival. The equinox brings the biggest tides of the year and as the incoming tide floods its way into the bay towards the river it causes multiple tidal bores, which converge and crash into each other in a dramatic spectacle known as ‘the silver dragon’.

Tidal knowledge and experience is vital at sea, when every second counts. At Red Bay Life Boat Station in Cushendall the RNLI volunteer crew work amidst the complex tides where the Irish Sea meets the Atlantic. Will they manage to calculate the tides and other factors correctly to rescue their affectionately named practice dummy ‘Dead Fred’?

Whirlpools are one of the most striking tidal phenomena. George Orwell’s son takes a boat trip on one of the most powerful, Scotland’s stunning Corryvreckan, which nearly claimed his family’s lives in 1947. Meanwhile at Norway’s fearsome Saltstraumen maelstrom, 100km north of the Arctic Circle, the tide conspires to give a highly experienced navigator the ride of his life.

Producer: Joanna Young
Executive Producer: Dylan Huws