Welsh surfing stars of the future are being trained on a giant wave off the coast of Pembrokeshire that has been compared to some of the world's best surf.

The Box, or Y Bocs in Welsh, which can reach a height of up to 40ft, has been labelled a European version of the waves off Hawaii.

To surf it when it is very big, you need a jet ski to get near it Peter Bounds, Welsh surfing coach

The wave forms in the middle of the Atlantic Ocean and travels thousands of miles, before it breaks three-quarters of a mile from the shore.

Peter Bounds, coach to the Welsh surfing team, said the wave was an excellent training ground for local surfers as they prepared for international competitions.

But he stressed that only experienced surfers should take it on.

"It is for experts only - there are probably only eight to 10 surfers in Wales who can handle it," he said.

"To surf it when it is very big, you need a jet ski to get near it," he added.

Mr Bounds said that he would be taking his team, who are currently gearing up for the Euro championships in November, out to The Box later in the year.

Surfers travel the world looking for the best waves

"A few sessions surfing this wave should help them prepare," he said.

"It is Europe's version of Hawaii," he added.

Mr Bounds added that Llantwit Major's Nathan Phillips, who is currently on the world tour, rated it as one of the best spots he has surfed in the world.

However, he said the team would be waiting until early summer to visit the wave again.

"We need the water to warm up a bit - surfing it in very cold can be even more dangerous," he said.

Fierce break

Mr Bounds, who runs a water sports centre in Dale, near Milford Haven, said the wave was not a new discovery, but that it was a well-kept secret.

It is a wave that breaks so fierce and so big it provides the ultimate challenge for a surfer Simon Alexander, surf reporter

"It has been known for 20-30 years and only one or two people have tried it," he said.

"I have surfed it, but not at its biggest," he added.

BBC Wales's surfing reporter Simon Alexander said The Box was a rare phenomenon.

"It is a wave that breaks so fierce and so big it provides the ultimate challenge for a surfer," he said.

"The swell has to travel thousands of miles to hit this reef, and then it all offloads its power in one go," he added.