TWO River Severn surfers are the stars of a new S4C show documenting the world’s most impressive tidal phenomena.

Llanw (Tide) filmed on four continents, taking in 10 countries and the Arctic for the series about the ocean’s tides.

And central to the series is the Severn, which has the third highest tidal range in the world, sometimes topping 15 metres (49 feet).

This range, when coupled with the Severn estuary’s funnel shape, forms the famous Severn Bore – a powerful wave which surges up the estuary twice a day.

And though the bore forms east of Monmouthshire – the river is far too wide for the wave to form until it begins to meander into Gloucestershire – it is a spectacle well-known around these parts, drawing surfers from miles around, as well as crowds of spectators and photographers, when the bores are particularly high.

Llanw features Severn Bore veteran Steve King, who lives over the border in Gloucestershire and has ridden the Severn Bore every day for the last 30 years, and Welsh surfer Tom Anderson, as they ride the waves through the countryside.

Mr King said: “If you are lucky you can ride it for half an hour or even an hour and the landscape changes all the time, you’re going through countryside with cows in the fields, and instead of an ocean wave breaking on the beach the Bore just goes on and on.”

And Mr Anderson said: “Surfing the Severn Bore is the closest thing that a surfer comes to having a spiritual experience.

“You don’t chase it, it chases you. It sweeps everything before it.”

The series, made by Welsh production firm Cwmni Da, also features the world’s highest tidal range, in Fundy Bay, Canada – where the difference between low- and high-tide can be as much as a five-storey building.

The crew also filmed in the world’s largest tidal bore, the 20 mph ‘Silver Dragon’ in Hangzhou Bay, China.

They also visited Norway to experience the world’s strongest tide, which has claimed the lives of 60 people over the years.

The first episode of Llanw was broadcast on S4C on Sunday (June 2) and is available online on the channel’s Clic catch-up service.

The series’ other two episodes will be broadcast on S4C on the next two Sundays at 8pm.