London - "Maybe it's escaped from the Princess Diana Memorial Fountain," is how one wildlife expert assessed the situation this morning.
Wildlife shots of the mystery beastie - definitely not doctored by the BBC or David Attenborough - show a Loch Ness type of 'monster' snaffling up a Canada goose as it skimmed the Thames outside the Olympic Stadium.
Early reports also blamed a stray alligator, a giant pike, a rogue turtle or even an out-of-control 'python'.
But whatever it is its presence is causing havoc for organisers of the 2012 Triathlon whose swimmers could now be re-routed from that stretch of the river to calmer, less-infestated London waters.
News of the sighting is also ominous for the Queen's Diamond Jubilee Thames Pageant which will feature a souped-up royal barge for HM and Philip.
Last night there were reports of a hysteria at Buckingham Palace after somebody told the Queen her boat 'could be sucked up by a giant freshwater squid'.
Fortunately a Royal Navy submarine armed with Stingray torpedoes will now be dispatched on a search-and-destroy mission.
Prince William may assist in his RAF chopper in case the operation somehow goes belly-up.