A goose-eating beast is lurking in the watery depths under the shadow of the Olympic Stadium, a boatman has warned.
Mike Wells said he had spotted a Canadian goose being pulled below the surface of the River Lea in east London, which "disappeared so fast it didn't make a sound".
There were reports of a goose being dragged under the surface back in 2005.
British Waterways, which is responsible for the upkeep of the river, asked people to report any further sightings.
Mr Wells, who estimated the weight of the goose to be about 7kg, said: "I was sitting on the back deck of my boat with a friend having a cup of coffee. And suddenly this goose about 30 metres away disappeared - it was extraordinary. We just saw the goose go vertically down - in the space of half a second it had gone. We don't believe there is a crocodile in the river. It was pretty surprising the speed with which it disappeared - and it didn't come back up.
In 2005 boat trippers on the River Lea watched as a Canada goose vanished "almost instantaneously", apparently dragged beneath the water by a mystery beast.
Mark Gallant of the Lea Rivers Trust, who was on the boat, said at the time of the 2005 incident: "Whatever that thing was, it had to be big."
A British Waterways spokeswoman said of the latest incident: "We don't believe there is a crocodile in the river. Things that have been suggested are a big pike or a mink, which can prey on ducks. But geese might be a bit big for them. In some areas you get terrapins which get dumped and have taken to the conditions well - they can get to the size of dinner plates. But geese might be too big for them to take as well. No-one has reported anything to British Waterways, but we would encourage people to get in touch if they have seen anything."
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