In our whole class discussion, our conversation was about the author's purpose. We decided that the author must really love the beach. She must know a lot about the beach too. Some kids even suggested that she may live at the beach. At the very least, they decided she must have visited the beach at some time and just wanted to share her excitement about it.
As kindergarten authors, we are doing the same thing! We are taking topics we know a lot about, and turning them into books. Of course there is a range of topics.
Prewriting, in kindergarten, looks very different than it does in older grades. Most of our prewriting is done verbally. One of my favorite ways to plan out a story, is to tell the story across your fingers. We touch our thumb and say the title of the story. The four remaining fingers represent one idea as well as one page of the book.
I'm working on uploading a video to demonstrate this.