Seth Casteel, the New York- and L.A.-based photographer who became internet-famous with his infectiously happy diving dog photo series, has taken things to the next level. His new “Underwater Puppies” photo series, which will be published as a book on September 16th, captures adorable puppies as they dive into a pool.

There’s no doubt that taking this photo series must have been heaps of fun, but it wasn’t all fun and games. “To create this series, I taught swimming lessons to over 1500 puppies, building their confidence in the water and helping them develop safety and survival skills,” says Casteel. “Most of the puppies only swam for a few minutes and were not ready for pictures, but some decided to start jumping in on their own and chase after toys!

More info: Facebook | littlefriendsphoto.com | Instagram | Barnes & Noble (h/t: time)

Seth Casteel’s book, Underwater Puppies, will be on sale at Barnes & Noble.