Imagine taking a sunset cruise and coming across this thing bobbing in the ocean. It looks like some sort of alien pod or giant mutant blowfish.

The picture was taken by Australian fisherman Mark Watkins, who thought it might be a downed hot air balloon until he got close enough to smell it. The stench, according to Watkins, was unbearable, which indicated to him that it must be a bundle of rotting biological matter.

Upon closer inspection, and considering the size of the stinky blob, Watkins knew it could only be one thing: a bloated whale carcass, reported The West Australian. But what kind of whale looks like this?

It turns out that the puffed up, veiny mass is the result of trapped gases inside the stomach of the whale, which probably expanded within its belly after days of floating upturned in the heat of the sun.

“It‘s stomach was full of gas so it was all bloated up,” explained Watkins. “When we got closer, we realized it had to be a dead whale because of the smell.”

This wouldn't be the first whale carcass found with a bloated, gassy stomach. And you don't want to be around when one of these fleshy orbs pops. Take a look at what happened when a sperm whale carcass was cut open by a Faroe Islands fisherman a few years back:

Luckily, Watkins was already headed back to shore before it burst, but the sharks Watkins saw nibbling on the carcass probably weren't so fortunate. He guessed that one of the sharks probably punctured it while taking a bite.

The species of the whale was not officially identified, but the texture of the belly indicates it was most likely a humpback or southern right whale, both of which are common in the waters of Western Australia.