The carcass of a giant sea monster washed up on the shores of an idyllic island in Indonesia. And the mystery of how it got there is just one of the questions about this curious creature of the deep.

What with its tropical jungles and gorgeous blue waters, Indonesia’s Seram Island may seem like a paradise. However, recently something washed up on its shore that looks like it’s been pulled straight out of a nightmare. And it’s not just the locals who have been confused by the giant blob; scientists have been puzzled, too.

The discovery was made by Asrul Tuanakot, a local fisherman. When Tuanakot first saw the shape bobbing around in the water close to the shore, he thought it may have been a grounded boat. But as he looked closer, it’s likely that he realized the massive thing in the water wasn’t anything man-made.

It’s easy to see why Tuanakot thought the mystery object could have been a boat. At almost 50 feet long, it was absolutely enormous, and it was nighttime when he first stumbled across it. Surely, though, it wouldn’t have taken him long to realize that what he had actually found was the corpse of some giant ocean beast.

Once the carcass of the creature was spotted, scientists moved in to obtain samples. And, judging from the decomposition of the giant body, they estimated that it had been dead for, at minimum, three days. Still, that didn’t answer the question that almost everyone who saw the images, or the corpse firsthand, was asking. Just what was it?

Next, the army moved in on the site, having been sent to guard the corpse and try to move it inland. After all, the carcass could well have been contaminating the sea around it. The giant mass was decomposing, turning the water around it a dark red color, and oddly the dead monster was floating as well.

However, that wasn’t the strangest thing about the corpse. After misidentifying the dead creature as a boat, Tuanakot revised his idea. There were what looked like tentacles splaying out of the mass of flesh – and that made him think there was a chance that it could have been a giant squid.

In fact, though, that couldn’t have been the case. Why? Because, along with the apparent tentacles, the dead creature also looked like it might have tusks. A sharp, white bone was jutting out of the mass, and giant squid are invertebrates: they don’t have any bones. Then, when the photos of the find started to go viral, marine biologists began to offer up suggestions.

Firstly, they debunked the idea that the monster could have been a giant squid. There have never been any reports of giant squid in Indonesian waters, so it is highly unlikely that one would have washed ashore. Thus, looking closely at the photographs and videos, the scientists came up with their own theory as to what the dead beast could be – and they were partly right.

Looking at the skeleton that could be seen poking through the rotting flesh – including a spine, a jaw bone and part of the skull – researchers believed they had identified the creature. The first piece of evidence that led to this conclusion was in what had previously been the creature’s mouth.

Yes, in some of the photos, there looked to be a baleen plate present. This body part is a component of the filtration system that a lot of whales use to separate the krill they eat from the sea water. So the corpse wasn’t a boat, and it wasn’t a giant squid. Could it, then, have once been a baleen whale such as a humpback?

That certainly seemed to be the most plausible explanation. And there were other pieces of evidence mounting up. The next piece of the puzzle came from what looked like so-called ventral grooves. This is the elastic tissue on the lower part of a baleen whale’s mouth that expands when it eats.

On top of that, there’s the geographical location in which the carcass was discovered. The Malaku Island group – of which Seram is the largest – is on the migration path of baleen whales. Hence, it was definitely starting to look like scientists had cracked the theory – and this meant that they could explain some of the other details of the story.

For example, while it’s rare, sometimes whale carcasses do float. More often than not, they drop to the ocean bed, where they’re eaten by other creatures. Indeed, a given carcass can actually feed a variety of animals for up to two years. However, under certain circumstances that doesn’t always happen.

In fact, a whale carcass will float if a build-up of gases inflates it. This could happen if the creature was hit by a ship or if it had a bacterial infection. It’s also possible that because the whale had died in warm waters, more bacteria may have built up inside it. This in turn would create more gas, which would help the carcass to float.

But there was another twist in the tale of this dead giant. While scientists around the world were examining the photographs and trying to explain what they saw, the Indonesian Ministry of Marine Affairs and Fisheries was also looking into the find. And though the ministry agreed with a lot of the suggestions, it came to a slightly different conclusion.

While the ministry did believe the find was a whale, it didn’t reckon it was a baleen whale. Instead, it stated that the corpse belonged to a sperm whale. Sperm whales can grow to up to 50 feet, which would explain the massive size of the carcass. Meanwhile, there was another reason for the ministry’s suggestion.

When a sperm whale dies and starts to decay, its intestines can protrude from the end of its throat. This is what gave the original impression that the corpse was a giant squid. It wasn’t tentacles that the fisherman had seen; it was the innards of the whale breaking through the rotting skin.

Now while these giant finds may stir the imagination, there are a number of factors that mean the ends of such stories are usually less dramatic than their beginnings. And although there are plenty of creatures that we haven’t yet discovered under the ocean, it’s unlikely that there’s anything as massive as this that we haven’t seen before.

Even so, just because this mystery has been solved, that doesn’t mean the story of the whale’s carcass has come to an end. The rotting mass of flesh is likely to be giving off some pretty nasty-smelling gases, and the red in the water isn’t just blood. As the creature’s body decays, oil from its carcass is seeping into the sea.

We’re sure that after the internet’s interest in this bizarre find has been sated, it’ll move on to the next weird discovery. But the people of Seram still have a pretty big problem to deal with. After all, cleaning up a 50-foot whale carcass that is leaking oil and full of noxious gases isn’t the sort of job you take on lightly.