David Cawkwell had been out on the waves for a couple of hours when he spotted the pod of up to 30 dolphins – including babies – swimming out at sea by the pier.

The dolphins seemed happy, diving out of the water and swimming around, so Mr Cawkwell moved closer, pulling out his mobile phone to capture some amazing footage of them at play.

He said: "I've been jet-skiing for years but never seen anything like this. You see one dolphin every now and then, but there were loads of them, about 20-30 in total. It was an amazing sight.

"At first, I thought they must have came inland because they were in distress, but they looked quite happy, jumping around and splashing about.

"I knew it was something other people might like to see, so I got out my mobile phone, which was in a waterproof case, and started shooting footage."

The 19-year-old window-fitter, from Baltic Court, South Shields, uploaded the footage to Internet video-sharing site YouTube, which has received more than 150 views so far.

Dolphins are known to occasionally leap above the water surface, but scientists are not certain why they carry out this behaviour.

Some believe it could be to locate schools of fish by looking at above-water signs like feeding birds, some say they could be communicating to other dolphins to join a hunt, attempting to dislodge parasites, or simply doing it for fun.

A spokesman for the Marine Conservation Society said: "Large pods of dolphins are often found off the West coast of Britain, but not so often on the east coast, which is why this video is so pleasing to see.

"The dolphins probably ventured closer to the shore because there's a larger concentration of fish in shallower waters."

Experts also say play is known to be a fairly important part of dolphins' lives, and they have been observed playing with seaweed or play-fighting with other dolphins.

They also harass other creatures, like seabirds and turtles.

In 2003, a school of dolphins put on a two-week show of tricks and jumps off the borough's coastline at Souter Lighthouse in Whitburn.

About 14 white beaked dolphins settled in the North Sea, drawing crowds from miles around to watch as they leapt out of the water.