On a moonlit evening in early May 2017, Asrul Tuanakota was walking along a beach when he saw something very strange floating in the water just a few feet from shore.

At first, the 37-year-old Indonesian man thought the monstrosity was a boat or a large man-made object, but upon further inspection, he realized it was a massive corpse.

When daylight came the next day, residents of Seram Island in the Indonesian state of Maluku found a hulk of floating skin, seeping blood and oil into the nearby waters. The being was approaching 50 feet long.

Initially, some thought the mass must be a giant squid. The creature had no obvious shape, so it wasn’t out of the question to think that the blob might once have been a huge invertebrate. Typically, Giant squid grow up to a maximum of about 45 feet, so this would have been an exceptionally large specimen.

Upon further inspection, though, it became clear that there were bones within the mass of skin. That ruled out the possibility of the creature being a squid.

YouTube user Anthony McDevitt watched a video of the carcass and shared some astute observations about the mass of skin and bones:

“I would say a humpback whale. You can clearly see what’s left of the baleen, so it is certainly a baleen whale. I say humpback whale for two reasons. The first is that long lower jaw bone. To me it looks like from either a blue or a humpback. But, what’s left of the upper jaw looks more like that of a humpback than a blue whale.”

A baleen is, as Wikipedia describes it, the “filter-feeder system inside the mouths of baleen whales.”

It seems as if McDevitt’s observations were pretty good. Alexander Werth, a marine biologist at Hampden-Sydney College in Virginia, confirmed with Live Science that the presence of “throat pleats” and baleen plates can narrow the creature down to a type of baleen whale.

Werth guesses that it was a blue whale or a particularly large Bryde’s whale.

In the same Live Science article, another scientist, Moe Flannery, with the California Academy of Sciences, insisted that the creature was not a humpback, although it’s not clear why not. Flannery thinks that there’s a chance that the blob was once a fin whale.

After the initial surprise and excitement of the discovery, people living near the beached whale were quickly ready for it to be gone. Bacteria must be thriving as the being decomposes in the in the warm equatorial Indonesian waters. In fact, it may have been bacterial bloating that brought the being to this very beach.

“If [a whale] dies in really cold, polar waters,” Werth explained to Live Science, “there’s a greater chance it will sink.” But if a whale dies in warmer waters, bacteria could thrive enough to keep the creature buoyant. From there, it was just a matter of winds and tides bringing the whale closer to shore.

At least it looks like this whale has already exploded, others that wash onto shore have been known to explode once the bacteria causes too much gas to build up in the massive decomposing creatures. That makes for quite a disgusting mess.