They usually spend their time in rough seas off wind-swept coasts waiting for the right wave but these surfers enjoyed a much calmer experience in an estuary of the River Severn in the UK.
They rode an unusually powerful, naturally-occurring wave called a bore.
The tidal range of the River Severn is one of the highest in the world and the large wave is produced when the Atlantic tide flows into the Bristol Channel and forces water into a tight space.
