Seals are swimming in the Tyne again after a clean-up transformed it from one of Europe's muckiest rivers.

Astonished Newcastle Quayside workers spotted a family of seals bobbing about in the river for a week.

The seals are believed to be looking for fish between the Millennium and Tyne Bridges.

Geoff Armstrong, 64, who lives near the riverside said: "I noticed them a week ago swimming about in the water and playing with things floating past.

"I haven't seen seals in the Tyne for at least five years."

The seals are drawing crowds of office and construction workers to the Quayside to watch the playful creatures.

Bob Watson, 52, an office worker at Quayside House, said: "I have been coming out to watch them for the last few days. They were coming right up to the Quayside."

"They seem to be really enjoying themselves."

High tide is the best time to spot the seals when they all gather together near the Tuxedo Princess floating nightclub.

Springtime brings spawning salmon into the Tyne and experts believe the seals may have followed the fish upstream, where they are in plentiful supply.

Dr Matt Bently, of the department of marine sciences and coastal management, at Newcastle University, said: "The Tyne seals are most likely to be harbour seals who live around the coast, particularly at the Farne Islands.

"They are very curious animals and will often swim up estuaries following trails of fish, especially at this time of year.

"There will probably only be two or three in the river and I suspect they have found a feeding niche between the two bridges."

Harbour seals feed on whiting, flounder, sea trout and salmon.

Harbour Seals can reach nearly two metres and can weigh up to 80kg. Their colour can range from brownish, to black with speckles.

The seals can dive to a depth of 300 feet, staying down for several minutes. They can also sleep underwater, surfacing subconsciously to breathe.

Dr Bently said: "If they've come from the Farnes they will be used to people and boats so they won't be scared to come into the Tyne.

"The Tyne is a good environment for them as a lot of fish swim into it and it is quite a clean river with lots of salt water at high tide. They'll probably return to sea when they get eye infections from staying in fresh water too long."