A huge, floating orb — one that looks more like an alien object than anything typically found in the ocean — left a fisherman perplexed when he came across it in the waters off the coast of Australia. But despite its strange appearance, the bobbing monstrosity has an earthly explanation: Researchers said it's a bloated whale carcass.

Fisherman Mark Watkins spotted the ballooned carcass about 30 miles (50 kilometers) southwest of Bunbury, Australia. Watkins said he thought it could be another boat or a balloon, but as he got closer to the orb, a pungent odor revealed the object's true identity: whale.

The species of the whale was not officially identified, but the texture of its belly suggests it was most likely a humpback or southern right whale, reported Mother Nature Network. [7 Things Most Often Mistaken for UFOs]

And though whale carcasses may seem like an unusual sight, they are a challenging problem. Marine biologist Andrew David Thaler told National Geographic in 2014 that the bloat of a dead, beached whale comes from pent up gas released as the animal's internal organs and stomach contents decompose. (Thaler created the website Has the Whale Exploded Yet? to update people on the status of a 375,000-lb., or 170,000 kilograms, beached blue whale in Newfoundland, Canada.) When jostled or manipulated, a whale carcass can explode, spewing whale guts and emitting a punishing smell.

"Imagine a jar of bacon grease that you leave out in the sun for weeks. Now imagine that odor is so potent that it clings to everything you own. ... Decomposing whale is one of the worst smells in the world," Thaler told National Geographic.

Beached whales do pose a threat to coastal communities. In 2014, an unusually high number of Newfoundland blue whales died and washed ashore, including the specimen Thaler was monitoring, after being trapped in shifting ice patches. If ice shifts in such a way that whales can't surface, the animals are unable to breathe and they can suffocate, reported CTV News. One or two animals are typically trapped in this way each year, but the nine whales that washed up on the Newfoundland coast in the spring of 2014 made for a particularly dramatic year, according to CTV News.

Thaler said the best option in the event of a beaching is to bury the carcass on site and leave it to decompose.

But whale deaths in the ocean, like what Watkins observed, result in a much more natural process. Thaler said scavengers aren't usually able to puncture the whale's thick skin and blubber when the carcass is floating in the sea, and eventually the body will naturally deflate and sink, intact, to the seafloor.

These events, known as “whalefalls," provide a staggering amount of resources for deep-sea creatures, and entire aquatic communities can thrive on the food a carcass provides, Thaler told National Geographic. The breakdown of a dead whale can take up to 30 years, he added.

Original article on Live Science.