A "horned sea monster" has washed ashore on a beach stumping marine biologists everywhere about what it could possibly be. The 13-foot creature was discovered by a female swimmer who came across the gigantic head at Villaricos beach in Spain, the Daily Mail reports.

Marine biologists and experts are mystified by the creature. The sea monster has a long white body, a slithery form and horns on its head. The body was already decomposing when the woman came across it and was reportedly giving off an awful, foul stench.

According to several reports, samples of the carcass were taken to be tested and the rest of the body was buried for "hygiene" reasons.

There are several theories as what the creature is. Some biologists believe it's an oarfish, a long deepwater fish that can grow up to 30 feet in some regions, while others think it could be some type of shark. Whatever it is it looks like something from a sci-fi movie.

"We have no idea what it can be, but it smelled bad, because it was so badly decomposed," Civil Protection Coordinator Maria Sanchez told Digital Spy. "A lady found one part, and we helped her retrieve the rest. We have no idea what it was. It really stank, as it was in the advance stages of decomposition."

The fish washed ashore earlier in the week and tests are still being done to determine what exactly it is. Florida State University ichthyologist Dean Grubbs doesn't think the creature is all that mysterious, Newsmax reports.

"That is definitely a shark skeleton," Grubbs told NBC News. "The elements toward the back were confusing me, but those are the lower caudal fin supporters. The 'horns' are scapuloccaracoids which support the pectoral fins."

David Shiffman, a University of Miami shark researcher who blogs for Southern Fried Science about marine biology also told NBC that he believed it was a type of shark.

"It's hard to tell," he said. "But the official guess that it could be a thresher shark seems plausible. Certainly the tail looks oarfish-y. It maybe could be a thresher shark - but nothing else."