casteel has found a remarkable new way to capture images of toddlers at their most playful and pure as they dive down into the deep during their first swimming lesson .
the pictures for his new book , underwater babies , reveal adorable babies as they explore the underwater world , chubby-cheeked , curious , mischievous , and playful , all captured in his up-close-and-personal signature style .
kids between one and four have the highest rates of drowning than any group in the nation .