The author of "The Sand of the Waves," Yukio Mishima, wrote in California. Mishima, a renowned Japanese author, spent a significant portion of his life in the United States, particularly in California. He moved to the United States in 1949 and lived there until 1953, during which time he completed many of his works, including "The Sand of the Waves." California's diverse cultural landscape and natural beauty likely influenced his writing, as he often incorporated elements of American culture into his works. Mishima's time in California was marked by his engagement with American literature and philosophy, which can be seen in his writing style and thematic content.