(CNN) -- Seth Casteel never expected his photos of dogs to make a big splash, but then again, he never expected one of his canine clients to jump into a pool during a shoot.
Casteel, 31, is the photographer behind a quirky collection of images of dogs caught in the act of diving, swimming, splashing and generally goofing off in the water. What makes the photos different from anything you've seen before is Casteel's perspective: below the surface, with the dogs lunging toward the camera in pursuit of a toy.
Dogs are an interesting subject, he says.
"They enjoy the benefits of 21st century living, staying in a warm house, sleeping in the bed with you," he says, "but getting in the water brings out the wildness in them."
Casteel's soggy dogs shot to stardom on February 9, when someone posted a few of his pictures on the social sharing site Reddit and they became an overnight viral hit, spreading to Facebook, Google+ and Twitter and in short order reaching 150 million views. His website (www.littlefriendsphoto.com ) crashed under the weight of a huge increase in traffic.
"By the morning of February 10 the pictures were everywhere," he said. "It just went nuts. It literally happened in the blink of an eye."
Suddenly he was receiving requests and offers from all over the world. One of those offers was a book deal from Little, Brown and Company, which on October 23 published "Underwater Dogs," a 132-page coffee-table book ($19.99) dripping with drenched dogs. A 2013 wall calendar also is on sale.
"I would have never known something like this could happen," Casteel said. "I went from not having enough work to having too much work."
Casteel said he wants to show the unique personality of each dog he photographs and tell its story.
"I'm interested in how emotional they are and how similar to humans they are," he said.
Before the shooting starts, Casteel spends time getting to know the dog and earning its trust.
"I show up, we start playing fetch, we become pals and we just move it to the water," he said.
Casteel wears a wet suit and snorkel mask, and sometimes uses diving weights to keep himself from floating. Then he tosses a toy and starts shooting.
He never knows what he's going to get. Sometimes it takes two hours in the water to get a good shot, as it did with a pug named Duncan. On the other hand, Duchess, the wide-eyed black Labrador on the cover of the book, gave him that stellar image within three minutes, he said.
"I could have a great shot immediately -- or not," Casteel said. "But that's what I love about it."
Some of the photos are downright frightening or otherworldly as the rambunctious animals bare their teeth and flail their paws in pursuit of an elusive tennis ball or other toy.
"You might get something silly or you might get something terrifying," the photographer said. "Some kids think those really kind of primal, edgy shots are funny."
The way Casteel got into dog photography is a story in itself.
"For me, it's been like destiny if you believe in that sort of thing," he said.
While working in advertising at Sony Pictures, he started volunteering at a Los Angeles-area animal shelter. Casteel shot flattering portraits of animals awaiting adoption, a departure from the usual shelter photos of terrified animals in small, dark cages. Nicer pictures, ones that brought out the animals' personalities, resulted in more adoptions, he said.
"We've gotten fantastic results from showing positive photographs," he said.
Soon after, he and a stranger cooperated to corral a stray Weimaraner that was running around on a busy road. After the dog was safely out of traffic, the men chatted, Casteel mentioned his shelter photos and the stranger hired Casteel to take pictures of his dog.
Referrals led to similar gigs. It was at one of those private shoots that a dog first jumped into a pool, and a new career was born.
(The New York Times recently hired Casteel to go to Alaska to shoot the sockeye salmon migration. A major difference between photographing dogs and photographing fish, he joked, is that "the salmon certainly aren't interested in a tennis ball.")
His work at the shelter also led Casteel to create a nonprofit organization called Second Chance Photos, through which he trains shelters in the art of pet photography. That work has taken him all over the United States as well as to Australia and Great Britain, he said. "I really enjoy it because it gives me freedom to explore what I'm passionate about."
"I don't even call it a job. It's my life," he added. "It's kind of a dream-come-true thing for me."