The Liverpool Echo has reported that a photograph snapped of an unknown animal in the waters of the River Mersey off Liverpool, England, has marine life experts baffled, all insisting that it is a different creature.

The image of this “monster” was snapped off Seacombe Ferry on May 25th, 2011, by photographer Mark Harrison. The photos show the back and “reptilian” head of a strange sea creature. A representative of the Blue Planet Aquarium, Paul Renolds, studied the unusual photos, but while he was unable to identify the creature, he was quick to presume that it must be a whale or dolphin:

“It is virtually impossible to actually identify, but this is the time of year when large numbers of basking sharks, the second largest shark species in the world after whale sharks, head towards waters off the Isle of Man… If it is not a basking shark, it could be a smaller species of whale or a dolphin because there are around 23 different species in UK waters.”

Harrison himself initially assumed that the creature in question must be a seal:

“At first, I thought it was a seal, then it disappeared under the water for a few minutes, coming back up further upstream and quite a bit closer. It was quite long and looked to be moving around slowly.”

Harrison was initially reticent to post his “Mersey monster” images online, for fear of being ridiculed. Sadly, this ranks as the most common reason for individuals to refrain from discussing their unusual encounters, even when there is photographic evidence. According to Harrison:

“There was only a few other people around, most of them in a hurry. I wasn’t about to stop anyone to point it out, because I didn’t want to be ‘that bloke’, who’s convinced he’s seen Nessie only for someone to point out it’s a big length of rope or something. Now look — I’m that bloke who thinks he’s seen Nessie.”

Danielle Gibas, an officer with the Sea Watch Foundation, leaned more toward the harbor porpoise theory — even going to far as to suggest that the case was solved:

“Harbor porpoises are notoriously difficult to spot. They surface fleetingly, and have such a small dorsal fin that it is often confused with ripples or waves in the water. Contrarily to dolphins, porpoises rarely leap out of the water so you have to be very lucky to notice them at a glance.”

Darren Naish of ScienceBlogs Terapod Zoology managed to refute both theories and present one of his own:

“A couple of days later, the Liverpool Echo stated that Danielle Gibas of the Sea Watch Foundation had ‘solved the mystery.’ Gibas, the paper says, said that the animal was actually a Harbour porpoise Phocoena phocoena. Sigh. The newspaper assumed that she was right. She isn’t, sorry… the photos show that the animal lacked a dorsal fin or vertical tail fin, they show a large water-filled gap between the animal’s back and head, and they reveal a squared-off snout with a flattish dorsal surface. These features alone immediately rule out porpoise or shark. Indeed, as was obvious as soon as the photos first appearedthe animal is almost certainly a Grey seal Halichoerus grypus.”

So what can we take from all of this? We have one “expert” from Blue Planet Aquarium suggesting that it is a basking shark, another from Sea Watch Foundation stating that it is a harbor porpoise and a third from ScienceBlogs who seems convinced that it is nothing more than a grey seal. Who do we believe?

I’m not suggesting that the Mersey Monster will not turn out to be a known animal — because it more likely than not will — but I would state that skepticism goes both ways and just because a so-called “expert” claims that the mystery’s solved does not mean that it actually is.