The gigantic carcass that washed up on the shores of Indonesia was so massive that witnesses first thought it was a boat. It turns out, it was just the mangled body of a mysterious monstrous creature.

According to a report from Jakarta Globe, the sea creature was a 15-meter-long monstrosity that attracted huge crowds of locals at Hulung Beach, Iha Village in the West Seram district. The carcass, believed to be dead for at least three days by the time it was discovered, was already beginning to decompose.

Local residents have reached out to the government to help them remove the creature's remains on the beach.

Initial reports defined the dead animal as a giant squid, but officials later concluded that it was more likely to be a whale. Specifically, a baleen whale, according to Alexander Werth, a whale biologist at Hampden-Sydney College in Virginia.

"There is lots of stuff in the ocean that we don't know about - but there's nothing that big" that remains unknown, Werth told Live Science.

Two distinct features revealed the identity of the mystery creature to Werth: the "throat pleats" and the upper jaw that would hold the baleen plates, which is used to filter food. While the scientists have confirmed that the whale belongs to the genus Balaenoptera, they aren't certain what species it is exactly.

In its advanced stage of decomposition, the whale would be emitting a foul stench due to all the bacteria in its guts. 

"That's yet another reason you don't want to be close to these things, not because it's a scary, spooky creature, but [because] it would just be releasing some pretty foul, noxious gases," Werth said, adding that it would not be wise to swim or drink the waters near the body.