Underwater babies: Zoe

All photos: © Seth Casteel

After making waves with "Underwater Dogs" and "Underwater Puppies," it was only a matter of time before award-winning photographer Seth Casteel would be back in the game with another project. This time around, he's exploring the world of swimming babies! Casteel was inspired to tackle this new project after learning a shocking statistic: Drowning is the leading cause of accidental death for children under 5 years of age in the U.S.

Cover of Underwater Babies"The hidden dangers of swimming pools continue to cause tragedies every single day, but these tragedies can be prevented," Casteel explains. "I saw photography as an opportunity to help."

With his beautiful new book, "Underwater Babies," Casteel hopes to encourage parents to learn more about the benefits of infant swimming lessons, which can reduce the risk of drowning for children under the age of 5 by 88 percent.

All of the babies in this charming series, including 5-month-old Zoe (above), are between 4 and 17 months old and were photographed during actual infant swimming lessons. At first, it might seem odd to give swim lessons at such a young age, but introducing your kids to an immersive water environment is quite beneficial at this age since a natural diving reflex (scientifically known as the bradycardic response) makes them significantly more resistant to drowning.

This important homeostatic mechanism causes babies to instinctively hold their breath when immersed in water (or during feedings to avoid getting milk in their lungs). In addition to the spontaneous breath control, this reflex also helps conserve oxygen when underwater by slowing the heart rate by 20 percent and reducing blood circulation to the fingers and toes. The bradycardic response usually wears off by the time babies hit their first birthday, so the sooner you can take advantage of this life-saving instinct as a learning tool, the better.

"Keeping our babies safe, whether they are fur babies or human babies, is our top priority," Casteel writes in the book's introduction. "They are our responsibility. We are their guardians. We are their voice. I urge anyone with a pet or a child to take all precautions to ensure their charges are safe around the water, and also to enjoy the magic that can happen when we partake in the water the right way."

Continue below for a peek at just a few of the shots featured in the book, and be sure to follow Casteel's latest updates on his website or Facebook.

Underwater babies: Ayla

Ayla, 7 months

Underwater babies: Michael G

Michael G, 12 months

Underwater babies: Zelda

Zelda Mae, 7 months

Underwater babies: Colton

Colton, 11 months

Underwater babies: Warren M

Warren, 11 months

Underwater babies: Adeline

Adeline, 10 months

Underwater babies: Valentina

Valentina, 9 months

Underwater babies: Michael R

Michael R, 4.5 months

Underwater babies: Emerson

Emerson, 7 months

Underwater babies: Khyleigh

Khyleigh, 9 months

Underwater babies: Claire

Claire, 7 months

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Catie Leary is a photo editor at Mother Nature Network. Follow her on Twitter and Google+.