New York Times bestselling author Seth Casteel taught thousands of puppies how to swim as part of his attempt to create the photography book "Underwater Puppies."

In 2012, Casteel published his first photography book entitled "Underwater Dogs" and it gained thousands of following from people all over the world.

Casteel explained that although dogs are born as natural swimmers, it is still important that they are trained well so they can adapt accordingly to swimming pools in particular.

After teaching the puppies how to swim, most of which were taught for the first time ever, Casteel decided to take snapshots of them while underwater.

The author/photographer also revealed his inspiration for the concept - none other than Buster, the cavalier King Charles spaniel he owns, NPR reported.

Back in 2010, Buster just decided, out of the blue, to jump into the swimming pool and he did so again and again. This sparked an idea on Casteel's mind to document the hilarious moment, thus leading into even bigger things in the years to come.

In an interview with the same publication, Casteel explained, "Puppies lift our spirits. They don't care who you are, what you've been doing, where you going, they just want to love you and they just want to be your friend. And I think that's always going to make us feel good."

Casteel's love for taking photos of dogs started when he decided to take photos of those who needed homes. Families immediately fell in love with his concepts when then helped the dogs find the best homes they deserve, the Huffington Post reported.

"The goal of the book was to feature some Amazing Rescue Puppy Ambassadors to remind people that adoption is a wonderful option! There are so many AWESOME pets that need loving families and I hope you'll consider bringing a shelter pet into your life," he wrote on his website.