Ecology experts fear a crocodile may be lurking in the waterways of Enfield after a Canada goose was seen being dragged under the water by an unknown predator in the River Lea.

Conservation officer for the Lea Rivers Trust, Mark Gallant saw the bird disappear before his eyes when he took a boat trip down-river to the 2012 Olympic site with representatives of the Inland Waterways Association.

He said: "When we were in the boat we noticed these large holes in the riverbank and wondered how they got there I flippantly said it may have been a crocodile.

"A few minutes later, we disturbed some Canada geese and one landed just ahead of the boat. Then, right before our eyes, it was gone. We all looked at each other and couldn't think of anything that could take out a Canada goose was it a crocodile?"

He added: "It wouldn't surprise me if there was an alligator or crocodile in the River Lea, because there are all sorts of creatures out there that have been pets and then released into the wild."

Since that first sighting last month, Mr Gallant and his colleagues at the trust have been researching other possibilities. He believes a more likely explanation could be that the beast' is an alligator-snapping turtle.

With the potential to grow to two-metres long, the fierce animals can be bought for £80 on the internet and are one of the main enemies of Canada geese in North America.

Mr Gallant said: "There have been reports of these being found in other waters in the UK.

"People put them in their ponds when they are babies but they grow very quickly, eat all their goldfish, and are then dumped in local waterways."

The Canada goose attack took place in a secluded part of the River Lea near Hackney Marshes known as the Old River Lea, but Mr Gallant believes it may have strayed up river.

He said: "The Old River Lea is a perfect place for these creatures to survive and probably many more similarly exotic beasts are lurking in the waterways and brooks of Enfield."

If you think you may have spotted the beast of the River Lea, call the Independent on 8362 1432.