Sammy the seal may have to swim for cover and Billingsgate Fish Market may have to spray some suppressing air freshener – a curious beast is patrolling the Thames in east London leaving onlookers baffled.

Youtube user Penn Plate filmed a squirming aquatic, er, thing while using the Emirates Air Line, its humps reminiscent of that other submarine enigma – the Loch Ness monster.

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The creature is clearly one of refined tastes for it presented itself by The O2, taking a gander, perhaps before submerging to the murky depths.

Penn said: “This was on the cable car in Greenwich yesterday. Something huge was moving under the water and then briefly surfaced. Are there whales in the Thames? Or is it some weird submarine?”

Seal in the Thames

The Thames has come alive in recent years with biological diversity with dolphins and porpoises not unusual, drawn by the wealth of fish. But the brief glimpse on camera – watched 800,000 times now – suggest something much larger.

Sadly, the footage only glimpses the object for a fleeting second but that shouldn’t stop anyone speculating wildly about the river’s new inhabitant – nor stop the beleaguered Emirates Air Line using it as a marketing tool.