A YouTube user in Chicago named Chris O has posted a 27 second video which he claims shows a hippopotamus in the Chicago waterway.

The video titled - Unknown creature seen in Chicago River believed to be a hippo - already has over 39,000 views.

At the start of the video two men can be overheard talking and one says, 'It went under again' while the other man tries to verify where it was initially seen.

The man then says, 'That boat is pretty much heading right towards it.'

Moments later the possible sea creature is visible again and the man says. 'There it is, there it is do you see it? The second man then says, 'Yeah, yeah, yeah, oh my god what is that?'

Despite the sighting of something in the water speaking with the blaze.com police officer Jose Estrada said there had been 'no reports of wild animals roaming the streets or the rivers of Chicago.'

The Chicago River is known to attract an abundance of watercraft such as sightseeing boats during the summer period. The video which dates back to September 15 is the only video uploaded by the YouTube user.

Calm: There is no sign of any creature during the early stages of the footage

Boat: As the boat comes under the bridge something moves in the water

Dark object: A dark object can be seen in the water as the boat approaches it.

Approaching: As the boat approaches the thing in the water the passengers on the boat seem to look at it