Dubbed the “Salish sea monster“, the creature was discovered by chance while Eric Evans was walking with his brother close to where the Elwha River meets the Salish Sea in the Port Angeles, Washington.
But after taking photographs of the beast and then showing them to wildlife experts, he was left none the wiser.
A spokesperson for the Washington Department of Fish and Wildlife said: “I shared the images and video with both fish and wildlife biologists in our department and we’re similarly stumped! Basically, the conclusion from our biologists is that this is unfortunately too far decomposed to identify.”