Diver Finds Giant Rotting Whale Carcass Being Eaten by Sharks

A diver managed to capture the incredible sight of a rotting humpback whale carcass floating at sea, as it was devoured by sharks.

Alejandro Castro, an amateur photographer, was diving off the coast of Mazatlan, in Mexico, when he spotted what looked like a small boat.

"We couldn't see what was going on, only that there were a lot of birds flying around it, so we thought it was a small fishing boat, so we decided to approach it because they might've ran into a lot of marine life that would be nice to film as well," he told Newsweek.

He was part of an expedition led by Onca Explora, comprised of filmmakers and marine biologists, who were searching for dolphins, when they came across a different animal.

Rotting carcass of humpback whale.
Rotting carcass of humpback whale. Amateur photographer Alejandro Castro captured the photos of the whale off the coast of Mazatlan, in Mexico. Alejandro Castro

Castro estimates the giant carcass of the humpback whale had been dead for two weeks, as he recalled the moment it came into focus, saying: "As we got closer, the shape of the boat started to change until we saw what was a yellow-ish carcass floating with a few birds on top of it and others floating around it.

"Our first thought was "I wonder if there are sharks feeding off of it", so naturally we got in the water with our cameras and started filming/ shooting photos.

"Whilst we didn't encounter any big sharks, we were in the company of baby silky sharks, and hundreds of mahi-mahi. Beautiful fish."

According to the NOAA (National Oceanic and Atmospheric Administration) Fisheries, humpbacks can grow up to 60 feet long and weigh 40 tons, with a lifespan of 80 to 90 years.

Rotting carcass of humpback whale.
Rotting carcass of humpback whale. He took the photos on Saturday, after initially thinking the shape was a boat. Alejandro Castro

Their main threats are entanglement in fishing gear, vessel strikes, vessel-based harassment, and ocean noise.

Castro, from Mexico, continued: "I'd never encountered a carcass before, no. My marine biologist friends were very excited about it because it's a pretty rare thing to run into.

"And the smell, well. On a scale from 1 to 10, I'd rate it a strong 15 haha! People who didn't get in the water with us pointed out that we were very smelly after we got back on the boat.

"The water around it had very good visibility. It was on the surface where we could see an oily texture floating, probably from fat leaving its body."

Castro took an incredible selection of photographs of the mammal, including both above and underwater shots.

Castro, who posts his images to his Instagram page @alexcstro, snapped the floating feast on Saturday, and shared the photos to Reddit's Pics forum, where they amassed more than 16,000 upvotes.

Rotting carcass of humpback whale.
Rotting carcass of humpback whale. Castro believes the creature was a humpback whale that had been dead for two weeks.

"Found a decomposing humpback whale carcass yesterday. Quite interesting!" he captioned the post.

The smell was strong enough for him to add a comment about it on Reddit as well, saying: "The smell was absolutely horrendous lol. And yeah, we were lucky it didn't have more than a couple of weeks, otherwise it would've been dangerous because they tend to blow up."

People were amazed by the spectacle, as Sturmhuhn wrote: "Something about things this much bigger than us being dead is just really unnerving."

Forevericeland raved: "Fascinating honestly. Not something most people will ever see in their lifetime."

Stelleypootz said: "It's a smorgasbord for all the fellas of the ocean, big and small."

Human_Robot commented: "Whale falls are some of the most fascinating things to me. They just create such an explosion of life it's wild."

As the Redditor pointed out, a whale death is somewhat of a big event for marine wildlife, and is known as a "whale fall."

The National Ocean Service (NOA) said: "When whales die and sink, the whale carcasses, or whale falls, provide a sudden, concentrated food source and a bonanza for organisms in the deep sea.

"Different stages in the decomposition of a whale carcass support a succession of marine biological communities. Scavengers consume the soft tissue in a matter of months. Organic fragments, or detritus, enrich the sediments nearby for over a year."

Meanwhile whale skeletons can support ecosystems for years to decades, as the NOA added: "At deep sea levels this forms a new food web and provides energy to support single- and multi-cell organisms and sponges, thus adding to the ocean's food chain."

Rotting carcass of humpback whale.
Rotting carcass of humpback whale. Castro said the smell was overpowering, calling it “horrendous.” Alejandro Castro