Marine biologist Simon Pierce happened to be in the right place at the right time to capture an image of a whale shark about to consume another diver, swimming near the surface with a snorkel, GrindTV reported.

Or at least that's what appears to be unfolding in the photo.

Pierce, a marine biologist from New Zealand, does research and conservation work on threatened marine species. His main focus, however, is the whale shark, the biggest fish on Earth, who are harmless to humans.

According to GrindTV, with the largest known aggregation of whale sharks in the world being in the waters off Cancun, Pierce witnessed 100 whale sharks swimming in the area when he dived into the Isla Murjeres in Mexico.

"I was trying to capture the shark's wide-open mouth, which was rather successful in this case," Pierce told GrindTV in an email. "Having the swimmer there gives some great perspective of the sheer size, too: This shark was about 26 feet in length. I had a 'fisheye' lens on for this shot, which gives an extreme wide-angle view, so the shark was probably only about a foot away from me as it passed."

With the number of whale sharks in the area, it wasn't a shock to see a giant mouth appear, Pierce added.

According to GrindTV, whale sharks feed on plankton filtered through large mouths that feature 300 to 350 tiny teeth and 10 filter pads, and stretch 5 feet wide.

"As long as it's not filled with sharp teeth, I'm pretty relaxed about it," he said of capturing the photo. "It may look like a dangerous situation, but it's actually just pure fun. You can see in the last shot, [the diver] already turned around to seek out the next customer."

Photos of the captured moment were sent by Pierce to GrindTV, to dispel any claims that it might have been photoshopped. "I don't even know how to use it," he said.

The photos were taken last summer but released publicly for the first time on Wednesday via Caters News Agency.

Pierce said he was leading a whale shark research expedition for his organization, the Marine Megafauna Foundation, and a group of marine tourists from Aqua-Firma U.K.

"My scientific work involves photo-identifying each individual shark from their unique spots, so my camera is a vital research tool, but there are so many sharks present that I allow myself a few more attractive images as well," he said.

The size of the whale sharks makes them highly photogenic.

According to GrindTV, they can reach up to 65 feet in length, weigh 66,000 pounds, likely live for more than 100 years, dive well over a mile deep, and can be fun for divers, though some discourage the practice of swimming near them.

"Because they feed on plankton, and are often quite curious about human swimmers, they're a very popular subject amongst dive tourists, who can swim freely with them," Pierce said. "In this shot, one of the guests on the boat was thoroughly enjoying this close encounter, but I imagine this sight was the last those plankton ever saw. The shark was completely unfazed by my presence, so I was able to capture this photo sequence as the shark continued to feed on the way past."

Take a look at all the amazing photos captured by Pierce here.